Car won't start. Not getting 12v power to starter solenoid

Please help! I have a 1999 Porsche 996 C-2 Coupe. It has just over 100,000 miles. When I try to start the car, it does not start. I have tracked back to the starter. I am getting current, but I do not get 12v to the solenoid when I turn the key. I hear the fuel pump prime. All the dash warning lights come on. All electrical work properly, but the starter will not turn and the engine will not fire. I have checked EVERY SINGLE fuse. I even tested with meter for continuity (sometimes a fuse will not look broken even when it is). I also checked and cleaned the ground strap on the passenger side of the engine. All the contacts (engine ground, starter and alternator) look clean and free of corrosion. Should I look for a starter relay to test? How is this done? What about the clutch pedal switch? Does anyone know how to check or jump the clutch pedal switch? Is there anything I am missing? Here is the history. Last summer, the car would start VERY VERY slowly once it was warm. As I understand, heat causes resistance, and after you drive the car for some distance, restarting can really stress an old starter or appear from a poor ground strap. This winter, I attempted to start the car in the cold. It started fine. Upon restart, it wouldn�t turn over enough to start the car. I had the car started with the aid of jumper cables, and I drove it to Auto Zone. Battery was charged and tested�passed with flying colors. Drove car home. Next day, car started but wouldn�t restart. It was the SAME THING, so we jumped it and I drove it home. Next day, I removed and cleaned the ground strap. Retested it�.car started but wouldn�t restart 20 minutes later. Then I removed the starter and alternator. Both were bench tested. Both passed all tests. I bought a starter anyway. After install, the car will not turn over AT ALL. I removed the new starter and took it back to Auto Zone to bench test. It engaged and started spinning and passed all tests. Then I put it back in the car and found 12v not going to the solenoid. So I bought a new ignition switch and installed that. I am still not getting any power to the solenoid. Please help me get this baby running.

I know you said you checked all fuses but please just check C1 to C4 again. Remove the two wires connected to the grey clutch switch and just connect the wires together and try again. That will bypass the clutch switch. Next is to check the starter relay behind the rear seats. Next is wiring between the relay and the starter solenoid. Once you get the car started, you can do voltage drop tests on the whole electrical system (including the Y" starter cable) to see if you are losing any voltage on any cables. The ignition switch is also known as a common failure.

Ok, I will check C1 - C4 again. Than I will bypass the clutch switch. And if those fail, I will check the starter relay. Is it hard to find? I don't know how to find it. I have been unable to find a DIY or a tutorial to remove whatever is necessary to gain access to the starter relay. Thanks for your help!

Just fold down the rear seats, lift up the thick carpet (carpet needs to buckle up in the middle), remove the driver's side aluminum panel, the relay panel is under it. The start lock relay is #7 here http://www.renntech.org/forums/topic...tion/?p=221230 Better get the wiring diagram to check the pinout of the relay.

Being that you have hard starts when hot, I would check the resistance in the engine ground cable and positive cable from the alternator. Both are known to develop high internal resistance that leads to hard starting, charging, or other issues. If you search the forums there are multiple threads on both.

I echo BBA. Even though the cables and contacts can look perfectly clean, they often become corroded on the inside. Especially right at the starter.

Thank you for all the great advice. I rechecked C-1 through C4 and actually hooked up each fuse to the full meter to check for continuity. All the fuses are good. Then I went to look at the clutch pedal switch. I jumped the clutch pedal switch and the car still not start. Then I check the relay. As soon as I engage the key and put it in the accessory position, the starter relay clicks. When I turn the key to engage the starter, nothing happens. The starter relay doesn't click and everything is silent. I was unable to get a wiring diagram to jump the relay. I figure I would just ask for advice to see if it sounds like this would be a bad starter relay. It sounds like somewhere between ignition and the starter relay, there is an issue. Is it possible that I reinstalled the ignition switch incorrectly? There were only two set screws and it was very straightforward to plug-in.

Although I sound like a broken record, it bears repeating: electrical gremlins in a 996 are often caused by a bad ignition switch. It is a $12 part that takes under an hour to replace, and some can do it in less than 20 minutes. So, start by first replacing any part that you suspect may be bad that costs less than $12 and takes less than an hour. Once you have replaced all of those sub-$12 parts, do the ignition switch next.

The way your relay clicks sounds normal. You can remove the relay and put a jumper (one that's good for a few amps) between pin 30 and 87 then try to crank. If that doesn't work, you can eliminate the relay and it's one of the follwings: - ignition switch not giving power - a break between the ignition switch and the relay - a break between the relay and the starter solenoid When you crank, 12v goes from the ignition to pin 30 of the relay. Pin 87 is connected directly to the starter solenoid. When the relay clicks, it connects pin 30 and pin 87 to prepare for your key to hit the crank position. Of course you can check if you get 12v at pin 30 when you crank and if you don't see it, it's one of the first two above. Wiring diagram here btw http://kt.qclt.com/porsche/manual2/p..._1999_2000.pdf

EEES, Did you check for corrosion inside the main power cables -mentioned above? You may have to strip back some insulation at both ends of each cable.If it is all green+ white powder -replace them. Or at least bypass them temporarily with a big jumper cable to prove the point. The corrosion problem is common as mentioned above.

We confirmed that the relay is getting power. My dad is electronic genius, serving as an engineer for a radio station, and he came over and we checked. You were right the relay is getting 12 V. As we connected the relay with a safety pin, it became glowing red almost instantly. It appears that there is no corrosion on the cables. It looks like we're getting current to everything except for the starter solenoid. I have suspected issues with my key for a while. I was going to buy a whole new one and have it reprogrammed. Is it possible that the mobilizer would prevent the starter from working? Or would that have caused the current to stop long before the relay?

The immobilizer sends power to the relay only if it detects the correct key is used. Since your relay clicks, that means the immobulizer is happy and all you need is power from the ignition to reach the relay. Were you able to make the engine crank with the jumper in place of the relay? Have you bench tested the relay? You are in good hands anyway with you dad being an engineer.

Sorry my previous post was almost unreadable (thank you, Siri). Anyway, the starter solenoid got no current with the jumper in place of the relay. I'm stumped. My dad told me to just take it to he dealer because I was likely to just add another unknown variable if I keep messing around. Any input would be greatly appreciated.

I reread your edtied post #11. Just to confirm, you removed the relay, jumped the pins corresponds to pin 30 and pin 87 on the relay socket, then you turned the key to crank. Jumper then gets red hot and starter does not crank. If the above is true, you do have current going through the stater solenoid but the stater is not turning therefore your starter solenoid is bad. You can remove the starter and get it bench tested to confirm. I don't understand though why you said you have no current but yet a red hot jumper.

You are correct. The jumper gets red hot, but the starter does not crank. Even though the jumper gets red hot, 12 v does not show up at the starter solenoid. As soon as I installed the starter a few weeks back, that's when this issue started. I immediately removed the new starter and took it to have it bench tested. It passed all tests, so I know the starter does work. Then I put the starter back in the car, and I have been trying to troubleshoot down the root cause of the non-starting issue ever since. I can't figure out why the jumper gets red hot at the relay, but there is nothing at the starter solenoid. The starter is getting 12 V, but the solenoid is getting nothing. Too weird ?????? Is there anything else back there (starter and alternator) that I could've messed up when I removed and reinstalled the starter and the alternator a few weeks ago?

Ok, can you remove the starter relay and the (thinner) wire to the solenoid, then check continuity between pin 87 of the relay socket and that wire at the solenoid end? Also check if the wire is short to ground. That wire connects the relay pin 87 to the solenoid to power it so by disconnecting the relay and the solenoid end, you make that wire float so you can do those checks. If that wire is shorted to ground, that will explain the symptoms you described. Then put the jumper in but leave the solenoid side disconnected, crank and see if the jumper gets hot.

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Your father is a wise man. Take it to a dealer and let factory trained technicians do what they are trained to do...get your car back on the road as quickly as possible. There are many here who gain some therapeutic benefit from spending days and weeks crawling through the guts of their car in search of mysterious electronic gremlins. This is a form of masochistic meditation and not to be confused with classical DYI issues such as change the oil and brake pads...or even rebuilding the entire engine. I myself prefer driving the car as much as possible and when something breaks, paying a trained expert to fix it.

Ahsai, thank you for all of your input throughout this process. We're going to do the isolation test on Tuesday. I will be crossing my fingers, and if that doesn't work, I will ship it off to the "stealer". John, you're so correct. There is a difference between doing routine maintenance and tracking down a gremlin. It just sucks when you create the gremlin. 😁

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We do have continuity between pin 87 and the starter solenoid. We tested continuity between pin 30 and pin 87 and there is none. The relay is toast. But did the relay just wear out, or was it because of too much resistance? That may explain why the relay jumper became red-hot within seconds of turning the key. The old starter was causing the car to crank over and over before starting, and eventually I wouldn't even start. When I had a friend jump the car, he had to rev his car to 3000 RPM to get my car to start even though my battery was just tested and charged. hmmm.... I have a feeling that the starter that I just bought is bad, as well as the original one. Even though Auto zone shows that both pass, there is a short to ground at the positive 12 V starter solenoid post. Sooo....do I need to get a new starter and a new relay?

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That's good. When the relay is not energized, there should not be continuity between pin 30 and 87 of the relay. Did you try to energize the relay? If you did and there's no continuity between pin 30 and 87, your relay is toast for sure. Did you check if the wire (after removed from the solenoid) is shorted to ground? The internal resistance of the starter solenoid is only 0.1 to 0.2 Ohm so it may appear it's shorted to ground. Can you remove the relay and jump pin 87 and 30 with a thicker wire like awg16? Maybe the safety pin didn't allow enough current to power the solenoid.

Is it supposed to be zero ohms between that pin and the case. Because that's what we have. Correction: it's very close to zero, but it's not zero.

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No, it's supposed to be very low but not 0.00 Ohm. I don't remember the exact number but I can check tonight when I'm home. I have a spare (but working) starter given to me by sjg1138.

Okay. Point one or two is close to what we have. That's good. A relay could make it work.

You don't have to go to all the trouble checking that. I can't thank you enough for all your help so far.

Yes, if you put 12v on pin 85 and 86 (polarity doesn't matter), the relay clicks and you got an open between pin 87 and 30, your relay is bad for sure.

We did energize the relay out of the car. It pulled it but no continuity between 30 and 87. It pulled "in". Let's put the starter back in and get a good relay. Should be good to go. BTW, no short to ground on pin 87.

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No worries as it's very easy anyway. I'll let you know as I'm curious myself too

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Thank you. I will definitely let you know.

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Since you have the starter out, you can bench test it if you're comfortable trying. All you need is a pair of jumper cables to connect the starter to a car battery, then use another wire (e.g., 16awg) to apply +12v to the solenoid, the starter should spin with gusto. Just be very careful dealing with the hot cables and make sure you hold the starter tight before putting power to the solenoid (sparks will fly).

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Raw power! The starter flies and the Bendix gear pops out. I take it back to AutoZone and add them retested on the bench. That way it was covered in a protective case Ordering the relay now. I should order "new" to prevent any more possible issues down the road.

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Haha, good. Yeah, I'm always amazed by the power and torque of the starter.

I guess it doesn't matter anymore now that you've confirmed your starter is working. I anyway measured one from a '99. I got 0.3 ohm between the solenoid terminal and the starter casing.

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I installed the new relay. Then I went to start the car, and it won't start. I'm stumped. I even put the old starter back in just to make sure that there wasn't some weird issue with the starter. All the lights on the dash come on. all the accessories work. I hear the click of the relay when I turn the ignition key, but then nothing happens. Then I release the key and about five seconds later I hear the relay click off. Is there anything in the engine bay they could be stopping the car from starting? I don't have all the connections put back together because I wanted easy access to the starter. I am half tempted to remove the alternator again. That's the only other thing that I messed with, but the alternator is on a different circuit and shouldn't affect the starter. Maybe an immobilizer issue? I would love to hear the starter turn over. Please help:-(

Can you remove the new relay and bench test it to make sure pin 30 and 87 close when energized? Then before putting the relay back on, put the car in neutral and try to crank it, check if you get 12v on pin 30 on the relay socket. The ignition switch sends 12v to that pin 30 directly when you turn the key to crank. If everything checks out, put the battery 12v (using a fat cable) onto pin 87 relay socket (relay removed) and that should start the starter. I agree the alternator circuit should not affect it as long as the fat 12v cable is connected to the starter.

One more thought. Are you sure the solenoid doesn't engage at all ? I wonder if it's possible the solenoid engages but the infamous starter "Y" cable is so bad that it can't supply enough current to the starter to spin. That "Y" cable is the cable that goes from the alternator to the starter then to the engine "+" jump start terminal right above the a/c compressor. That cable is known to fail and I've replaced mine twice. When it goes bad, I lost 0.7v on that 2 feet cable when 50A is going though it. However, I never had problem starting my car though even when the cable was bad. Not to say it can't happen. https://rennlist.com/forums/996-foru...ter-cable.html To verify, you can do a v drop test between the battery "+" terminal and the starter power terminal (the one that connects to the "Y" cable). When you crank, either you will see 0v if the starter is not even getting power or something low like 1-2V but if you see anything higher, that means the starter is not getting enough current. Also I assume your battery is still in good shape? BTW, should also check the engine ground cable behind the right rear wheel.

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The relay closes when energized. Also, we are getting 12 V to pin 30 when I turn the key. The rest of the tests are a little more advanced then I can do by myself. I'm going to have to wait for my dad to help me tomorrow. Thank you for all the help. We're going to solve this.

Ok, at least you're sure the ignition switch and the immobilizer are good. The new relay is most likely good (pending bench testing) and your starters work OUTSIDE of the car when you jumped them. So that leaves the yellow wire to the solenoid and the fat wire (the "Y" cable) to the starter and the engine ground wire.

Alright so we worked on the car again today. We checked the relay, and the relay is actually bad. Something fried it. I pulled out the alternator again and we checked the Y cable. Forgive me of my lack of vocabulary when it comes to explaining electrical tests. We checked checked the ground strap, and all other possible components to ground. Everything was excellent, and we have continuity from the battery all the way back to the Y cable. We checked everything! Then I went and got another relay at the auto parts store. We tested the relay and the relay tested well. Then we plugged it into the car and tried to start the car. Again, nothing happened. Then we took the relay back out and retested it. The relay was toast. So, I have toasted three relays. Is it time to take this to the dealer or does anybody know why I am going through relays with the turn of the key.

This scenario did cross my mind when you mentioned your red hot pin hence my suggestion of testing pin 87 on the socket shorting to ground (chassis). You need to remove the relay and disconnect the starter solenoid to isolate that yellow cable to test it. Did you check that? That's the only logical explanation left.

We did check continuity from pin 87 to the wire lifted off the solenoid. We did have continuity. We do not have short to ground. Then we disconnected the solenoid wire and checked pin 87 to ground and got .2 ohms, which I understand is normal. Any ideas?

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The 0.2 ohm is not normal. That's short to ground! With the solenoid wire and relay removed, pin 87 should float and not connect to anything else. Am I missing something?

Oh wait. I said the .2 ohm was with the wire disconnected. It was actually connected to the solenoid. No short when disconnected.

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Oh wait. I said the .2 ohm was with the wire disconnected. It was actually connected to the solenoid. No short when disconnected.

This is baffling. You have already eliminated a lot and I don't know how much more you can test. Since your relays (the power contacts side) keep blowing and your starters work outside the car, I have to suspect you have a short to ground somewhere after pin87 toward the engine. However, you said you tested that wire and there was no short. How about if you remove the wire from the solenoid and connect that wire to a 12v light bulb (e.g., 55w headlight bulb) instead? The light bulb itself would not blow a good relay and you can see if power is delivered. You may also want to take apart the blown relays and see if they are repairable.

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Oh brilliant! We will try that (and recheck the wire as well to confirm there is no short). Dad is taking one of the relays to the station tomorrow to inspect the relay. I will keep you updated. Your level of knowledge on this topic is really amazing.

BTW, I've attached the relevant wiring diagram here for your reference (with some drawing of my own). "YE" means yellow. The number next to the color is the cross section surface area of the wire. e.g., "4.0" means 4 mm square. You can see there are two thinner "2.5" wires between pin 87 and the solenoid. The reason is the "X59/1" connector can only carry wires of that size so we need two "2.5" in parallel to match the "4.0" wire from the ignition switch to pin 30 of the relay. "4.0" is good for 32A and "2.5" is good for 24A. My current suspicion is you have a short to ground on the wires between pin 87 and the solenoid or your autozone starter (1.1kW) is too weak to turn the engine. The stock starter is rated at 1.7kW. Porsche-996-starter-circuit.jpg

I did not read the whole story, but had a starting problem, on my 84 3.2 Carrera, and it was just a VERY dusty , dirty, starter, run fine after a good clean up! done in S Luis Obispo. Cal. during a cross country /camping road trip back in 07, That was ONE great trip !! mmmmmm

Ahsai! You are outdoing yourself with this thread and spiralling that wagon towards a final solution very nicely for this poor guy. Good on you and thanks for the many tips throughout.

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Anytime! Just trying to help out here. I think his case is quite atypical yet interesting.

Rereading post #1: I put my $$ on bad "Y" cable. Corrosion under the insulation by one of the crimped connectors. "Here is the history. Last summer, the car would start VERY VERY slowly once it was warm. As I understand, heat causes resistance, and after you drive the car for some distance, restarting can really stress an old starter or appear from a poor ground strap." "This winter, I attempted to start the car in the cold. It started fine. Upon restart, it wouldn�t turn over enough to start the car. I had the car started with the aid of jumper cables, and I drove it to Auto Zone. Battery was charged and tested�passed with flying colors. Drove car home. Next day, car started but wouldn�t restart. It was the SAME THING, so we jumped it and I drove it home." Rereading post 15: Sounds like something connected wrong, or shorted to ground during installation. "As soon as I installed the starter a few weeks back, that's when this issue started."

Yes, the "Y" cable and ground cable are not ruled out at this point yet. To prove those cables are bad, a voltage drop test on the cables is needed, which requires large current flowing through the cables. Without the starter or the engine running, the only way that I know of is to put load on the engine end of the cable (e.g., use a carbon pile battery load tester). If the starter is not getting enough current, it will not spin and that may blow the relay. The two terminals on the starter are of two different sizes so I don't really think you can put the wires on wrong. OP is going to test out the short to ground solenoid wire. If there is NO short, the problem has to be in the starter and/or the cable(s). The OP already confirmed the engine can be turned by hand so it's not seized.

Its always the "Y" cable. If it hasn't ever been replaced, it needs to be (along with the ground strap).

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So do you guys think the "Y" cable can also explain the car blowing up the relays? I think it's possible but not 100% sure. At least I have not heard of such cases reported online.

It is always the Y cable and the ground strap. So has anyone got a suggested upgrade for theses two problematic parts? More corrosion-proof connectors ,better sealed insulation at the ends of a ground cable.Use an old fashioned braided strap so you can see corrosion ? Ashai - you are just amazing at helping to resolve these obscure issues. Thank you !

Ahsai, I haven't pulled a 996 starter yet. Is/are there any insulated washers/bushings that keep the hot feed from touching the starter/solenoid housings? I'm thinking something like the insulator on the points spring stud that would drive folks crazy if the spring was slid behind instead of in front causing a short, no spark, that kept the coil energized even when the points opened.

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Hi Frank, no, there are no such bushings. It's almost impossible to have an external short. Also, the solenoid and the 12v power posts are of different sizes so it's impossible to hook up wrong. Anyway, the latest is he was able to start the car with the autozone starter and all the stock cables connected with the addition of a jumper cable connecting the starter 12v power post and the engine compartment "+" jump start terminal, essentially bypassing the y-cable (if it's bad). However, later on the car also started after he removed that jumper cable Anyway, I chalked that up to an intermittent y-cable failure and suggested he replace it. image.jpg

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The ground cable is not so much of a problem and usually it's due to age so replacing it with the stock one should last you a long long time. The y-cable is a different story. It's cooked by the engine all the time. I already had two failed on me. Both were the latest version. The second one failed in less than 2 yrs and it was still shinny when I removed it! If it fails again, I will put in a new one with all the crimps sealed with dielectric grease. The good news is I can replace that cable in an hr or so now. I replaced my alternator in 20min last time

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Now I'm wishing I sealed the crimps on my Y cable when I put it in. I did put dialectic grease down in the area between the insulation and the cable with the idea being that the grease would keep out the moisture and help prolong the life of the cable. Maybe sealing the crimps completely would solve the problem. There has got to be a way to make a Y cable that won't fail.

Looks like pretty standard internal contact solenoid activated lever arm starter. Hope he posts pics of the "Y" cable so we can see corrosion/shorts etc...

Anything new here? I am getting ready to head down this rabbit hole myself. My 2004 GT3 has intermittent starter issues. I've replaced the ign switch, battery, and checked both ground straps. All good. The car does start, but sometimes it takes 5,6,7 attempts for it to catch. The battery maintains a charge, so I'm now thinking it's a starter issue. Thanks for any updates to this thread.

Yes, the OP was able to start the car with the autozone starter and it looks like it's an intermittent issue with the y-cable. You said sometimes it takes a few times for the engine to catch. Does it mean the starter spins at normal speed but the engine just won't fire up? If that's the case, one strong suspect is the crank position sensor. Does it happen more when engine is hot? I assume no stored error codes?

Thanks for the response! The engine fires right up. It's like there is sometimes nothing when I turn the key. I then turn key back to 0 and turn back to start again, sometimes it fires right up sometimes nothing. The starter motor never spins on its own without the car starting right up. I can go back and forth several times before the starter engages, then motor fires up immediately both hot and cold. I don't believe it's a hot cold thing but I will be more cognizant of that, although I am afraid to take the car out if I plan to stop somewhere, imagining it will not start again. I have also checked the clutch switch and it appears fine as well. Thanks for you valued assistance. There are no codes that show up at all.

Ok, I know you said you checked your clutch switch (gray) but it can also fail intermittently. I would just remove the clutch switch and jump the terminals with a paper clip and drive the car like that for a few days and see. Of course remember to put it in neutral before starting now that the safety is gone. If it's not the clutch switch, since it's intermittent, you will need to wire a light bulb to the starter solenoid terminal or at least to the start lock relay pin 87. Make sure you can see the light bulb when you turn the key. The bulb should turn on everytime you crank. If it does not, it means the solenoid in not getting power. If it lights up but the starter does not engage, then it's very likely the starter solenoid is not moving despite being energized.

Clutch switch appears to be the culprit! I jumped the two wires and presto, the car has started every time so far, and best of all I don't have to depress the clutch any longer. I'm not sure if pulling this switch out of service has any other ill effects, but I always confirm the car is in neutral before I start the car anyway, so not having the switch is a plus for me. I will drive the car around and get it hot and confirm this was the problem, but it feels more direct when the car starts, and I feel this is the likely solution. Many Thanks!!!! I'm pumped that this may be it. I will confirm in a few days when I am sure it's completely fixed.

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Your odds are pretty good I would say If you have a digital multimeter that beeps when testing for continuity, you can bench test the clutch switch. Keep activating it on and off. If it fails intermittently, you will hear a scratchy beep or no beep at all when activated. Hard to catch that with the resistance setting where only the resistance value is displayed.

Christallon, Thanks for posting that Ashai's fix worked. It is frustrating when we work with someone to fix a problem over many,many posts and then they just disappear. We're left wondering, did it fix it, did he die trying some stupid fix, what? The best part is that Ashai's fix is simple and clean and requires minimal expertise/tools//risk/equipment. Once you start removing chunks of wiring for testing/inspection and stripping insulation all sorts of complications arise. Most important, Kudos to Ashai who is so helpful,patient and competent !

Kudos to Ahsai !

An ice cold brew and please raise your bottles to Ahsai Many Thanks Man!!! Rennlist Rocks, as do you! Schnell Gelb, funny ****e there, I almost lost most of my swig of beer, through my nose laughing at your post. So true!!!

Thanks guys! Glad to help out and love to virtual wrench/trouble shoot

Thanks for all the great info in this post. I have a similar issue, and I must be missing something. My car always started when cold. When hot, it would sometimes do nothing, but within 5 tries it would always start. I didn't start it for 10 days, and when I returned, it doesn't turn over. Battery still had 12.4v. All dashboard lights as always, just doesn't turn over at all. Battery is new and good (12.4v) Clutch switch jumped (even though it tested good) Ignition switch seems ok, never had any issues Starter relay is good. Also tried a new one. (powered the relay, heard the click, and resistance was .01) Pin 30 on the relay socket has 12.2v when turning to the start position If I jump 30 and 87 on the start relay socket and hit the key, the starter turns I checked fuses C1-4 and E1, visual and continuity. All good Cleaned and checked engine ground. Seemed ok, continuity tested good. I will replace when I get one Replaced Y harness, as I thought this was the cause of it failing to start when hot. It didn't solve the problem I didn't think of checking the trigger wire on the solenoid, or anything else while I had access. Rookie mistake, as I had convinced myself it was the Y harness. Any ideas? Thanks in advance. 99 C2, 100k miles Tim

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Sounds like the issue is strongly correlated with temperature. Was all your troubleshooting done when the no crank occured? If not, it will be hard to draw conclusions. I suspect the starter or the ignition switch but since it's intermittent (it would fire up on the 5th try even when hot), one way to prove it is as follows. Wire a small 6w bulb between pin 87 of the starter relay and the ground. Place the bulb where you can see it in the rear view mirror when you are cranking. If the bulb lights up, that means the ignition switch, dme, clutch switch, and the relay are all fine and the starter solenoid should get power. So if the starter is not spinnng, that means the starter solenoid is most likely the culprit (given the new y-cable). If the bulb doesn't light up when you crank, then your problem is in one of those items listed above. Using the same principle, you can wire an LED (with a 600ohm resistor in series) to the coil pins of the starter relay. Note the correct polarity, pin 85 negative and 86 positive. That will tell you if the dme is activating the relay.

Thanks Ahsai. Yes, all troubleshooting was done when this no start occurred after sitting in the garage, 75-85 degrees. I do have an ignition switch that I'll get in today, and I'll try the light thing. Thanks again.

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Btw, you can also usr a wooden stick to tap on the starter solenoid when it doesn't turn over. It could be a sticky solenoid. Also, did the dash light dim at all when you cranked and it didn't turn over?

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Thanks again. No, the dash lights don't dim. The ignition switch was replaced with a new one, same results-doesn't kick over the starter. Still have 12v at relay 30. Thanks for the reminder on the stuck solenoid, and a starter is on my list (since the initial issue seemed heat related). So why would the starter kick on the first try everytime when I jump the relay, but not when the relay is in? If it kicks when jumped, wouldn't I at some point found a non dead spot on the starter? Over the course of this past week, I have tried to start it 30+ times with the relay in (no kick ever multiple relays that still test good) and 4 times with it jumped (kicked everytime). Thanks for the response. Tim

Ok, with more info like that, it sounds more like the dme not activating the relay (but you said you felt the relay clicked though). When you jumped the relay, did the engine fire up? If it doid, it means the dme recognized your key (transponder pill) correctly. Did you ever try a different key? Note the relay should click as soon as you put the key in the last position before crank AND you pressed the clutch all the way.

Hi Ahsai. When I jumped the relay, it did not start, just turned over. Although I was just doing that to check the starter, not trying to start it. But it normally fires right up, and it didn't. I only have one key. The clutch switch has been jumped almost the whole time of diagnosis. Thinking about it now, I guess its possible I heard another relay click when in the run position. I just reconnected the clutch switch, and did not hear the relay click when I pushed the clutch all the way down (I did hear the clutch switch). Interesting side note, since I replaced the ignition switch earlier today, the radio won't turn on (aftermarket unit). Thanks again.

To be sure, can you confirm when you jumped the relay, all you did was removed the relay and connected pins 87 and 30, then you just turned the key and cranked the car like normal? If that's the case, the engine should have fired up like normal. If It did not, your problem is the dme was not in a ready state so it did not activate the starter relay. That could be because of the clutch switch or the key transponder recognition. Btw, you can still hear the starter relay click when it's far behind you plus with the clicking sound of the clutch switch at the same time? Would help if someone else can place a finger on the relay to feel it clicking when you put the key in the last position before crank and press in the clutch. How's the integrity of the key fob and the transponder inside?

Yes, I removed the relay, connected pin 30 and 87, hit start position, it turned over but never fired. As mentioned above, after reconnecting the clutch switch, it doesn't seem like the relay is clicking upon the on position and pushing in the clutch. I do need to verify this again when I get some help. Reading up on key fobs, it really does seem like a key fob issue. Integrity is marginal as the internal pins holding the plastic halves together don't hold it together anymore. No signs of water or corrosion. The remote part also doesn't work. I had talked to the shop about getting a second key, and planned on doing it when I had chance. I think I waited too long. Thanks

The important part for starting the engine is the transponder pill inside the key fob. The remote is something separated. The reason is there's a coil in the ignition key hole that reads the pill and the pill needs to orient and position correctly for the coil to pick up the signal correctly.

Yeah, I wasn't too worried about the remote not working as I knew the pill was separate. Thanks again for all the great info. I'll update when it gets to the shop to make sure the pill is still being read.

If the jumper is getting red hot and your starter isn't getting power, that to me sounds like you've got a grounded +12V wire.

Hi 5ch3ll. Thanks for looking this over. I think it was the guy before me that had the hot jumper. Mine was fine and when in place, the car turned over, but didn't start. Think it's the pill/immobilzer. Funny story. So I hauled it to the shop today. The mechanic unloaded it while I was in the office telling my story. He walks in with the key, opens the semi broken fob mentioned above, and there is no pill in it. Gone. It must have fallen out at some point and I didn't realize it (had it taped shut although the tape wasn't sticking that well). Scour the car and my house, can't find it anywhere. The wife, kid and dog all look guilty but aren't admitting to anything...yet. New pill, reprogram and second key coming soon. Tim

Tim said: " I have a similar issue, and I must be missing something ?"Post 70 Post 82 - Answer to his question - Yup, missing the PILL from the key ! Thanks for telling us Tim. We now need to add this issue to all the othersthe Diagnostics list for the "no start" threads - make sure there is still a Pill inside the key! Thanks for letting us know.

Hi All - Ahsai suggested piggyback this thread on not starting - this one is a really strange one that's got us all puzzled! Porsche dealer now looking at it - fault is atypical! 1. Intermittent starting problem – car cranks once not crank more will not start a) Drive car for 30-60 minutes, park the car for 1-2 hours. b) Return to start the car but the car will not start c) Engine cranks once only – not continually crank but not start d) Sometimes if lock unlock car with key fob the car will start sometimes will not start at all e) No faults on durametric computer or on dashboard, no flashing lights or CEL error f) Disconnect battery for 24 hours sometimes works ok as car will then start when reconnect the battery After numerous checks my garage came to conclusion that DME / Immobiliser was broken. Sent to ECU doctors for repair, who confirmed damaged so got this repaired. Fitted to the car and now another problem on top of above! 2. Driving problem – car engine suddenly switches off when driving a) Driving car after 20 mins driving suddenly engine switches off b) Dash lights come on as if just turned key before ignition, no flashing lights or CEL error c) Restart car fails per intermittent starting fault above cranks once won’t start d) Sometimes if lock unlock car with key fob the car will start sometimes will not start at all 3. Parts investigated / changed a) New Ignition lock, DME repaired, New Immobiliser, New Keys, New Battery, New fuel pump b) Relays checked / swapped when car would not start, still didn’t start

Thanks for continuing here to get some fresh eyes. One thing to add is yours a 996 TT and it's a TIP. Your problems are indeed very strange. For your problem #1, I had suggested wiring a small bulb to the starter solenoid circuit so at least you know when the starter stops, whether it's due to power cut to the starter solenoid or the starter stops on its own. For your problem #2, fuel pump is the usual suspect but that still can't explain why the engine cranks once and then stops.

Thanks Ahsai - yes 996TT and TIP Yesterday was stuck in the middle of the road so didnt get a chance to test. Weirdly after a few attempts, lock unlock car then try again it cranked fully and started and then drove for 1 km before stopping again and same starting issue. I can't say now if lock / unlock is this coincidental or related e.g. wait a few mins something resets / cools down. So if starter motor then you're right #1 - would be starting issue but then car stopped dead when driving #2 could be fuel pump but then started again after wait / lock / unlock and drove no problem. note fuel pump was changed about a year ago, less than 5k km I wonder if something is shorting out somewhere, or the whole immobiliser dme thing was a hoax? Could be something else e.g. crankshaft position sensor - but then we read that would mean cranking not start - not crank once stop when cranking not start Strange!

How many volts are showing on the volt meter on the left side of the dash? If below 13 it is too low. I had intermittent issues with the car turning off while driving (only when the car had been driven for a while) which was resolved by installing a new alternator Y cable. All lights on dash turned on also, no check engine light or codes appeared. If your volts are low let us know as the culprit is probably y cable, voltage regulator on alternator or alternator.

The notorious Y connector is an obvious suspect and in these circumstances a part to just replace w/o bothering to test. Why? The part is suspect,cheap ,easy to replace and the fault is intermittent and potentially dangerous .You could spend hours fiddling and never come to a conclusion. So just replace it - imho. I had one experience like this .The fault was an intermittent ground fault with the immobilizer. An intermittent ground fault at the DME may produce this problem? But to diagnose, the fault must be present and remain present throughout the testing - which is impractical as a diy when the car stalls in the street.So part substitution is probably the best strategy ? Not a clever suggestion ,I know but.....

100% agreed with the above.

The alternator voltage check is a good suggestion. Regrading the y-cable, keep in mimd this is a TT, which has a different design. See this diagram http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996t-99-05&section=902-05 You can see that there are two long cables from the battery to the starter directly, then there's a shorter cable that connects the starter to the alternator. If the shorter cable is bad, the battery cannot be fully charged. However, that short cable shouldn't affect starting directly as it doesn't supply power to the starter during cranking like our n/a 996s do. If that short cable is bad though, it should reflect on the voltmeter in the dash. The normal voltage should be 13.5v to 14.5v whenever the engine is running with some load such as a/c and headlights.

Thanks all for the suggestions - will send them onto the dealer They called me today to say now the car wont start at all - its doing the one crank then stop - which is different from when I left the car for towing = car would start but stop after about 5 mins driving I'm guessing the computer won't pick up the fault and I do feel its something like wiring or something Question - ecudoctors said my dme immobiliser were corrupted / damaged. Any clues why that would happen e.g. would Y pipe defect or an earth shorting out make this problem - if so which earth or wire?

Voltage drop test is the only way to confirm a bad cable/connection (unless you have obvious corrosion on the wires). I think the good news is now the issue in persistent and that should make the diagnosis a lot easier. So currently the car won't crank at all or it cranks but won't start?

ok Porsche came back They said alternator intermittently low voltage output Not sure this quite adds up eg yes when driving engine stops that could be a cause? But why would car not start or crank - note previously when this problem before towing they put on battery pack to get car started but still same problem Surely more likely wire problem eg ground wire?

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That is interesting. While you were driving, did you notice your voltmeter in the dash read low sometimes? It should be between 13.5 to 14.5v whenever the engone is running. At cold start, it should read ~14v once the engine started.

Good question - I know it was around 13 from memory including when it wouldn't start let me ask I will go see them Monday - I want to understand how they identified voltage output was intermittently low If they can prove checking properly not just random guessing - that's definitely showing a problem Its identify what is the source eg I doubt alternator likely as people said the y pipe / ground strap per part 36 here correct? http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996t-99-05&section=902-05 My suggestion then would be change this wire first and rerun the test before try other things

Where are you located and how long have you had the car for? Are you 100% positive your car was never in a flood before? If so, corroded connectors/wiring could have the various intermittent effects that you are describing. Did you remove the immobilizer yourself? If so, did you notice any dirt or rust in the connectors?

Based in Hong kong Car hasn't suffered flood damage and immobiliser was removed from car by my garage im going to get Porsche to closely inspect the wiring

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Maybe they took it out for a test drive and saw the voltmeter on the dash fluctuating around the low level but I agree you should check with them. Yes, that's the ground cable. Should be very easy for them to check it both visually and electrically.

Yes, that's the ground cable. Should be very easy for them to check it both visually and electrically.[/QUOTE] Maybe worth let me know how to test in case they're s bit lost . I noticed this link for a 996TT but not sure how accurate - seems to have a number of tests? http://www.renntech.org/forums/topic/44306-my-last-report/?page=1 or is this post more useful that posted some time ago? http://www.renntech.org/forums/topic/44471-voltage-regulator-affected-by-heat-hence-low-voltage/ thanks again!

Basically they can perform a voltage drop test on that cable but they should know and if they don't, you don't want to have your car repaired there anyway. For a complete check for the whole system, check out this link http://www.renntech.org/forums/topic...arging-issues/

Yeah tell me about it - I took the car to Porsche hoping their computer and tools, specs, data etc they'd know how to pinpoint But now they've said alternator doesn't really add up vs symptoms so I'll question them today - see if can show me voltage drop in action, did they carry out these tests - HK are notorious for replacing things on trial and error basis - at owners expense My other mechanic might be better option eg real mechanic (they rebuild trannies etc) I can be there do all the testing with him eg test wires and replace as required plus can send the alternator and starter off for testing. He did say could be crankshaft sensor but only thing can do is replace difficult to test Only worry is will the car stop in between garages! Ill keep everyone updated

I understand your situation. It's not very different here in the US anyway. One "good" news is if your engine cranks but not starts consistently (like claimed by the dealer), that would be a lot easier to diagnose. Regarding the crank position sensor, one quick way to tell is when you crank watch the tach closely and see if the needle bounces 1/8" inch or so when the engine is cranking. The bouncing indicates the DME recognizes the signal from the sensor. If there's no bouncing at all, it's likely you have a sensor/wiring issue. However, if there's bouncing it's not conclusive because the signal could be bad even if it's present. One will need an oscilloscope to check the waveform. To test the ground cable quickly, you can hook up a fat jumper cable between the car chassis (e.g., the brass metal jump start point in front of the airbox and the engine (i.e., any metal parts that directly connect to the engine such as the exhaust system or the engine brace). If the engine starts w/o problems with this cable in place, then the ground cable is a strong suspect. One thing to note is diagnostic requires special skill set than pure mechanical one so not just any real mechanic will do, even if they rebuild engines or trannies. I know there are shops specializing in diagnostic in HK but I have no direct experience with them. Can you ask the PCA (or equivalent) in HK who they would recommend? I would expect the Porsche dealer in HK be better than that. The intermittent engine stop when driving will be quite challenging to troubleshoot but I would expect they could at least diagnose a no start and/or no crank car.

Ok great - I met with someone referred to me he agreed not alternator - also pointed out to him with your diagrams what are chief suspects he he said will test ground and power wires alternator and starter olus crankshaft sensor - as Porsche do have the specs and tools to test Not clear if car still not starting but I said that just run at idle for 30 mins until powers off then test lets see what they come up with!

Ok so Porsche cleaned up ground cable on chassis side - said driven car many times over 30 mins - engine didn't stop and car starts no problem - we're hoping that it's not just something else intermittent eg they did resistance check on crankshaft sensor seems ok but ground cable seems a big clue however voltage still low around 11.5 not 13.5+ So I've said replace ground cable first then retest eg if that doesn't fix voltage problem then can look at alternator and check power cable whilst replacing eg could be do both will update again next week

If it's truly 11.5v, you have a better chance of a bad alternator/regulator because a bad cable will most likely rob you 0.5-0.7v. It's a problem that needs to be fixed on its own regardless of the starting/no-start issues anyway.

Update - ground cable changed - then after some testing car didn't start again just turns over once as before The voltage is still low - so we know at a minimum that the alternator isn't working we are going to change it. I suspect this is why the car stopped when driving eg not enough volts from alternator and battery trying to run the car with aircon lights on etc They suspect starter motor problem for starting crank once issue - I think we can test this without take it out first to bench test if car won't start now eg light bulb to starter, when car won't turn see if power still sent to starter?

Sounds reasonable to me.

I hope so! Taken some time for them as they relocated shops That and need to test as they are worried the car will just stop when driving Do you have more details of the starter test they need to do eg I guess they'll use multimeter - where to connect wires etc - they should know but just in case! Will likely replace alternator, power cable and starter if it's faulty - may change crankshaft sensor as well as precaution

Diagnose, don't flail - the OEM alternator is very expensive !! Alternator - it may be just the Voltage Regulator (search). Ahsai has an excellent link to an better+cheaper alternator - he may like to comment? Here is the link? http://www.renntech.org/forums/topic.../?_fromLogin=1 It is a 997 alternator # Bosch AL0815N Are you really,really sure the battery is in perfect condition ?

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There are two yellow wires from the start lock relay pin 87 (behind left rear seat panel) that connect to the starter solenoid via the X59/1 plug (pins 24 and 25). They may want to start from the relay or that x59/1 plug (the top big round one in the rear right engine bay) if accessing the starter solenoid directly is difficult. If they replace the alternator, I assume they will have some access to the starter though. I would check the voltage there when you crank the car and see what voltage you get when the starter stops turning. WONGY has a TT Tip so not sure if that alternator will fit though. It may but I just don't know. It's worth checking for sure.

Ok long time since update! Porsche kindly loaned me a 2015 Cayenne Turbo whilst order party's carry out testing on the car Just picked the car up today - changed alternator - power back to 14v cold 13.5+ when warm As precaution / preventative measure I also asked them change power and ground cables, crankshaft position sensor, battery was changed as well given not been charging properly for some time Early days I'll need drive it more but at least volts didn't drop after 45 mins drive and the car didn't stop when driving, plus started ok on a few occasions Fingers crossed thanks to to everyone for posts and especially Asahi for advice much appreciated - I'll post again in a few weeks on how things are going

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That's good news and glad you got it sorted!

Update: starting problems all gone and no engine stopping during driving however noticed misfire recently - computer faults P0491/P0492 says SAI or vacuum leak - since SAI is cold start and working ok eg hear running first few mins, assume vacuum leak given low rpm 1-2k stumble though it's intermittent im suspecting that since these parts are same area as alternator maybe vacuum pipe is lose? will need get garage to inspect the system to check

Thanks for letting us know Wongy. With all the work done on your car, perhaps a vacuum connection was accidentally separated ? Before you start removing parts again, I suggest a little research on ways of locating the leak with the engine idling. The usual method is spraying (carefully!) carburetor cleaner or using a small unlit Propane torch.You can add a hose on the end to get to the really difficult areas.

Make sure the vacuum hoses are connected, and since you had your alternator replaced, check your oil filler pipe for cracks.

thanks my garage said there are many vacuum pipes? im wondering does this fault code helps identify that it's the pipes near where the SAI is fitted in the car? i would guess a vacuum leak would mean the car doesn't run as good as expected?

Imagine a plate of black noodles - that is your vacuum system ! Ahsai has a photo of the system that he posts sometimes. https://rennlist.com/forums/996-foru...omponents.html That is why I recommend propane as a diagnostic tool.It helps find the location of the leak.Accessing that area is the next problem ! Yes your car will idle badly with a vac leak. see post 44 here: https://rennlist.com/forums/996-foru...ml#post7967422

Update SAI pump was loose so was vacuum hose plus boost hose was missing Very strange as to why can only think not put back properly - but all fixed now And the car hasn't failed to start or had voltage issues since the power earth cables and alternator replaced

Bad news and very frustrating Been drive car for six months no problem with starting yesterday starts no problem - 14v drive for 30 mins park up as usual cone back to car and won't start battery just below 12v, but even booster from tow truck won't start porsche need check but can only assume it's blown alternator again which was the problem last time luckily it has 2 years parts labour warranty I wonder could something be damaging the alternator eg already changed the +/- cables in engine bay?

How old is the battery? Also, once the car has sat overnight put your hand on the alternator and see if it is warm. If it is, then the voltage regulator in the alternator is bad. You can change just the voltage regulator, but since you have a warranty you could just get a new one.

I was lucky to get my car for a bargain price because it had similar electrical issues. I trailered it home. The first thing I did was charge the almost new battery at two amps overnight and install it in one of my other cars. I drove around for several days while I did further diagnosis and waited on parts. The battery worked flawlessly. In parallel, I took the ground cable located behind the passenger rear tire off the engine and body and made sure both ends were good and clean along with the mounting points on the body and engine. They were. I cleaned both battery terminals and they looked good. I disconnected the battery negative terminal cable at the body and bingo, the connection to the body was bad. I cleaned the cable connector and body mounting connection thoroughly. A bad ground will kill the voltage regulator, and then the rest of the alternator. The prior owner gave me the original alternator and I took it, along with the almost new alternator that I took out of the 996, down to the local Advance Auto Parts. They put both alternators on the tester and they were both dead. Typically when you have a bad ground, like I did, the voltage regulator goes bad and the alternator will put out 17+ volts, when it should be about 14.5v, which will boil the battery and kill it. In my case, the voltage regulator was dead and the new alternator was putting out less than 3 volts. The original alternator was rebuilt by a local shop that rebuilds thousands of alternators each year (United Rebuilders in Seneca SC). They specialize in Bosch and had all the parts on hand. The original 996 alternator has an aluminum clutch-less pulley. Porsche apparently recognized a problem with shredding accessory belts on manual gear box cars during high RPM deceleration early on and they swapped to a clutched pulley. I stuck the rebuilt original in a box as a spare and ordered a correct rebuilt Bosch alternator with the clutched pulley for about $400 from Pelican Parts. The almost new alternator that was installed when I bought the car was a Chinese Bosch replica with the standard pulley so I didn't get it rebuilt. While I was waiting on the Pelican Parts alternator, I installed the battery and measured the voltage drop between the battery and the terminal where the alternator attaches (the end of the "Y" cable that also attaches to the starter) and the engine case. The drop was 0.3v (from about 12.5v at the battery to 12.2v), which is expected. I also inspected the terminals at the back of the starter, which are relatively easy to get to when the alternator is out. They looked good. Note that my car has spent its entire life in upstate SC and has never seen a salty road. The starter sounded good the few times it was jumped, so I did not get it rebuilt at United Rebuilders. I will do that when I pull then engine out. I installed the Pelican Parts alternator and the car has run well ever since, except for the central locking that doesn't work correctly and will drain the battery if I let it sit for three or four days, but that's a separate issue. One thing I should add is that everything worked on the car when it had the bad ground, but the starter was a little sluggish because there weren't enough amps passing thru the bad connection and the alternator died, of course.

The car had new battery alternator engine ground and power cables installed 6 months ago the garage tested the car - cold start 30 mins drive park up. Then try restart won't - and by that I mean car cranks once then stops like run down battery but it's not . Alternator pushing healthy 13.6v when warm and battery ok they tried put new starter in same problem now looking at wiring said something about ecu to ignition missing messages codes? But the ecu was tested refurbished a year ago when first find this problem and immobiliser with keys changed there can't be much more left in the starter circuit eg cold start runs ok - if ecu problem it wouldn't run properly strange problem

Really thought you fixed it for good a few months back. It's indeed a strange problem based on what you described. I agree that it can't be an ECU problem. It's more like the engine/starter is somehow hard to turn when heat soaked. One thing you can try is to jump start it when it doesn't start. If it starts with jump start, there's still issue with the battery or charging system. If it doesn't, can try to manually hotwire the starter. If that still doesnt work, that points more to a mechanical issue of the engine/starter. Try to turn the engine by hand and feel for resistance. If normal, the (new) starter is the only thing left.

Thanks Ahsai - yes I thought all sorted too as its been good for last six months , though the alternator was clearly broken given low voltage output it's defo something been triggered due to heat soak - after towed to garage they started it no problem 1.5 days later. They drove for 30 mins, switch off then on and wouldn't crank - note that's the key point it not that car cranks not start it cranks once then stops we tried jump start with power pack same problem. Sometimes it would crank once, then next time just not crank at all when turn the key they said starter motor initially - I think they changed to new one tried it didn't work This is what he said "We found there are some errors from and missing the main ecu which leading to mis-communication with battery control. Our techs are now measuring the wirings one by one see where goes wrong." when first had this fault we sent ecu immobiliser for testing, got new immobiliser keys and cleaned up ecu - has 5 year warranty so I doubt that's the fault Could it be wiring as they say? I'll ask them check the battery ground wire though it looked ok not dirty, also ignition switch though changed that before otherwise difficult fault to find

If it is the DME, the starter should not spin at all. Wiring is possible but it's unlikely given the heat related symptom. The usual suspects including the starter and the starter cable have already been replaced and jump start has no effects so that's why I suspect the engine itself or anything it's driving on the belt.

Latest from my dealer. Not sure it adds up eg because when I first had this problem the ecu immobiliser and keys were sent for testing and refresh to ecudoctors who gave me a new immobiliser and ecu was cleaned up and tested. The car surely wouldn't run even if bypass if ecu broken? that and ecu is obviously very expensive - but I've told the dealer prove it works first. Seems it's their strategy remove replace parts see if it works thoughts? "After all the tests done these days, we found the starter and ignition run after bypassing the main control unit but we would like to make it certain, a new main control unit is ordered and delivering to us by courier. Hopefully it will be arriving early next week and i could provide an answer to you. Sorry for keep you waiting and thank you for your patience."

Wongy, I was just reading this thread and noticed that this is a job that we did for you at one point. In your message above you said that they are "bypassing" the "main unit". Do you mean the ECU? If you have the invoice # of your job I can look at more details from my side to help you.

I already sent a note to lee pennant ecu doctors directly 8/6/17 at 10.33am EST - maybe you'd like to review there and reply as appropriate given the part is supposed to have a 5 year warranty

Resurrecting this thread. First, thanks for all of the great clues thus far! 1999 Boxster. Problem started when ignition switch failed. Car was running great, then the ignition switch broke internally. The accessories stopped working in "on" and I couldn't completely turn to the "off" position. Could not remove key, and went part way back to "on." had to disconnect battery with key in ignition. I replaced the switch the next morning with a standby (leftover from replacing a good switch before I diagnosed a bad starter). Car started right up with the new ignition switch. I turned it off, and removed key. Next morning all lights on dash, but no 12v power to starter. Here's what I've done so far: checked fuses C 1-4 and F1, installed another (new) ignition switch, bypassed clutch switch, jumped 30 to 87 on the starter relay and starter and solenoid tuned the engine over just fine, but won't fire up. I replaced the starter relay and no change. If the key is turning the engine with the jumper wire in place, isn't my key being recognized by the immobilizer? What should I try next?

I assume you meant fuse E1 (there's no fuse F1). With the jumper wire between start lock relay 30 and 87, the DME is bypassed. Power flows from the battery to the ignition switch, jumper and then the starter solenoid directly. So that only means your ignition switch is good. You can try the following: - another key - retrace your ignition switch work and make sure all the connections are tight - use Durametric to scan for code

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Thanks for your reply. Yes, sorry, E-1. Sadly I only have one key. I am confident in the switch work, so I ordered a Durametric tool from EBay. If jumping the start lock bypasses the DME I'm thinking it must have something to do with the immobilizer. I have tried to reset it in the two ways suggested: lock and unlock the door 3 times with everything shut (my mechanic), and lock and unlock the car with the key in the ignition. Neither worked.

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Right, jumping the relay will bypass the DME, as shown in this wiring diagram here .

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Received the Durametric. Plugged it in, but it can't find any fault codes. The only information I can get from it is when I check the A/C, is says it isn't communicating with the DME. Getting ready to give up and tow it in. I think it must be the key not being recognized, but I don't understand why that would not throw a code.

Generally speaking, the starting circuit(s) will not throw codes, and are difficult to diagnose. Remember, codes (P-codes) are related to running parameters, such as O2 sensors, misfires and MAF sensor faults - emissions related stuff. The immobiliizer, key RFID read in the start sequence is not something that will throw a code.

That makes sense. Thanks for your response.

There's also a fuse on the immobilizer ifself (under the driver's seat). Have you checked that?

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Not on mine. I pulled it (quite a PITA!) and there is no fuse, outside or inside. I do not have an alarm system, which may be the distinction.

Perhaps open up the key fob and check/clean the transponder pill. Can't think of more things to try at the moment.

Re-check your connection at the immobilizer antenna (plastic ring around the key cylinder) and the signal convertor ( black box mounted on the steering lock).. make sure they are properly seated. Wiggle them while trying to start.. Did you have these disconnected while doing your ign switch? Seems likely it's something to do with the ign switch replacement, and these are in the area...

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I didn't disconnect them during the switch install - at least not knowingly. I will check those. Thanks!