2002 C2 Cabriolet Won't Start, Fuse C2 Pops, All Conditions

2002 C2 Cabriolet, car died while driving. Pulled over found fuse C2 (Ignition, Fuel Injection, O2 sensor heating) popped. Unplugged O2 sensors, C2 still pops regardless of key position (or insertion). Removed Relay number 1 on secondary relay support tray, fuse does not pop. Unplugged DME, re-installed relay, fuse holds. Waiting on tow, but next steps are to unplug variocam solenoids with DME unplugged and plugged. Then ignition coils with dme plugged and unplugged. Engine does turn over at normal rate. Any thoughts?

Mice got into the rear harness where it comes into the car(behind coolant bottle or other side) causing a short? It sounds like the issue it in the wiring?

Quotes source post: 20464438

Almost guaranteed to have no mice here. Assuming its the wiring harness, I have a new (to me) engine harness. The question is, can I replace it with the engine installed?

It really could be anything. U should get a wiring diagram and start testing the affected circuit for a short to ground. Its a teadious process but its how u find the issue. I would not replace anything until u find the short. Unplug (isolate) everything that c2 fuse connects too. If it still blows then its in the harness. A good meter, a set of spoons for back pinning and time is all u need.

Quotes source post: 20464829

That's the plan. I've pulled the DME and inspected, no sign of electrical damage.

You should be able to figure it out. Break out the wiring diagram and start checking loads on C2. You'll have to uplug whatever you can one at a time and check for resistance to ground. Right now you are seeing less than 5 ohms, you need that to be a big number, at least 2000 ohms if it is going through loads that have a path to ground with the voltage of a multimeter, but I would imagine it should be much higher than 2000 ohms. You got this! It's going to be something obvious when you find it considering it died while driving.

Quotes source post: 20465015

Unplugged almost everyting (All 4 variocams, all 4 o2 sensors, 4/6 injectors (the remaining 2 are difficult to unplug, but the wires are visually okay and I don't believe it is the fuel injector wiring.) There is some chafing on the variocam wiring, but I have the wires separated to prevent shorting. C2 pops when applying power with the key, or until the car "powers down". Until it powers down, there are about 9 volts on the variocam solenoids. If I pull C1, C2 will not pop and the variocam voltages drop to zero, so I am assuming it is somewhere in the c1, c2 relationship. I wonder if I should just replace the harness, since I have it on hand, but I don't want to completely drop the motor.

Unplug the large connector to the right of the motor. Not sure which one the c2 runs through. If it still pops its before the motor harness or in the o2 harness as they dont through that plug. (I think its the x51 connector?)

I'm getting ready to shoot the pins on the x59/1 and x59/2 connectors. Barring chasing all the wires in the wiring diagram, does anyone have a pinout for x59/1 and 2? Comparing the Bentley manual and AlldataDIY or the PDFs I have of the wiring diagram, there seem to be some inconsistencies, for example the Bentley lists a X59/3.

Troubleshooting results: Left X59 = lower connector with white circle and no pin on 20. Right X59 = upper connector All testing was performed on the removable side of the X59 connectors (female). Both X59 removed - fuse intact Left X59 removed / Right X59 installed - Fuse Blows Right X59 removed / Left X59 installed - fuse intact (right causes fuse to blow) The following pins are making contact with ground. X59/right - 1-6, 16-18, 23-25 X59/left - 16,17 There was some power steering fluid residue in the right connector which I did spray with contact cleaner on both the female and male sides.

So the right side plug harness is the issue between the fuse box and the plug. This rules out the engine harness and sensors. Sorry at work today(snow day yesterday) so i cant check the diagrams. I just use the Bently and u have never had a problem tracing wires. Should be able to determain which wires travel from c2 to the x59 plug.

Quotes source post: 20465846

Forgive me for any misunderstanding I am definately not trying to argue or disagree. If both connectors are removed, that eliminates the wiring going to the actual engine (injectors, oil pressure sender, coils, etc), right? My thought is that if both are removed and the fuse is intact, then the wiring harness (99660701010) has the issue, correct? It would appear to me that the vehicle side (male pins) leading to the DME are good. All DME connectors and relays are currently reinstalled. Please correct me where I may be wrong. Thanks again for the help!

More troubleshooting - Ignition coils are still connected. They were just replaced, so I am assuming they are good (I know, don't assume). On the right harness connector (female): Pins 1-4 - < 1ohm Pins 5-6 - 11-12ohm Pins 16-18 - < 1ohm Pin 23 - 3-4ohms Pins 24-25 - < 1ohm Disconnecting coils 4-6 results in pins 2, 6, and 18 becoming open circuits. The question is, which connector is X59/1 and which is X59/2? I'm assuming that X59/1 is the right connector since that is where I am testing and the pins seem to line up.

Quotes source post: 20465828

You have done a a logical step by step process of elimination.By eliminating what is not the problem you've narrowed it down considerably to what may be the problem. You are making good progress. After your troubleshooting above you've eliminated the left side harness completely and everything it is connected too So now we know your problem is on the side of the disconnected right side plug that when plugged in causes the fuse to blow. So any wire(s) devices, switches, or controls, etc, from the disconnected plug to all the devices connected to it are the possible problem. Now you have to test each one of those. Or if you got one of these LV circuit breakers off Amazon you could de-pin one wire at a time, plug connector back in and see what pin causes the fuse to pop... A $5 low voltage circuit breaker will prevent you from going thru dozens of fuses. Some come with the wires that will plug right in to the fuse socket with their spade connector. The below one in my pic I made up the wires/connectors//terminals. It pops open when amps are to high, then you just push the button back in and good as new... They come in all different amp ranges just like fuses do. I use these in all types of LV control voltage testing without constantly having to change out new fuses. Amazon Amazon

Quotes source post: 20465990

I have some of those resetable fuses that I have been using in place of the c2 fuse. Same 30A rating.

Yea sorry i just reread. U r right the issue is on the engine side of the harness. Continue on with your diag...u will find it.

Quotes source post: 20466117

No worries, further troubleshooting: Made sure that all O2 sensors, fuel injectors disconnected, variocams, ignition coils are disconnected. With X59 right plugged in, still pops. Latest resistance testing (everything disconnected): Pins 1-3 OL Pin 4 - < 1ohm Pin 5 - OL Pins 6 - 11-12 ohm (Injector 2 is not unplugged) Pin 7-22 OL Pin 23 - ~4 ohms Pins 24-25 - <1 ohm I can't imagine where it might be, other than the known chafing, or maybe something was knicked/kinked chafed when I reseated the engine from my idler pulley repair.

I can still connect via PIWIS and interrogate the DME, so are we safe to say that the DME is not the issue?

I would bet its not the dme. I would really have to spend some time looking at the schmatic to help. I try to find some time this evening.

Quotes source post: 20466253

Thanks, I'm taking a break from it for now, but will be exploring just replacing the engine harness. I'll need to get the engine out with the quickjacks, but I don't have SUV adapters, so it may be tricky.

I have a partial harness from DC Automotive that is missing the left connector. The right appears intact and when plugged in the fuse did not blow. Obviously it was not connected to any components, but it does show that there are no shorts in this harness. A new (to me) one is on the way and I am just going to swap the harness, and inspect the one I pull off.

Just take a break. You have two pins that are a short to ground. You don't know if they are suppose to be a ground or they are grounded. That's where your issue is. You need to use a multimeter from here and refrain from energizing anything, you'll just do further damage. I have been busy, but I could look at the schematic in the morning. You are so close.

Sorry it was a long day and i did not get to my schmatics. Maybe tomor?

Further research. According to schematic, pin 4 is the 87 leg on the ignition/oxygen sensor relay and 24-25 run to the starter via the Start Lock Relay. The starter runs fine, but pin 4 connects to CP2 12A/E2. Need to figure out those assignments.

[Image-only post; no author-written text. Original image references:] https://cimg4.ibsrv.net/gimg/rennlist.com-vbulletin/1540x2000/img_0468_c73d10e8ff8144e315b5c12ae9f76676f1827784.jpeg

Quotes source post: 20467348

Thanks! That's super helpful. Do you know what year it covers, if there are any differences?

There may be differences as this is for my 99. should be accurate for the most part.

When I look at the 996.2 wiring diagram, it doesn't show the X51 pinouts. I just looked at the 99 engine sitting in my shop outside of the car, and the X59 connectors have a few pins that don't have any wires in them. It sounds like yours are all full but one. Can you pop off the plastic cone on the back of the connector and let us know what color the wires are that have issues? Then we can look at the ECU wiring diagram and match up the loads. If you can take a picture and let us know if the wire is a "regular size" or "large size" wire, that would be helpful.

Quotes source post: 20467858

Pin 4 is a larger black wire. I edited a prior post, apparently i did not disconnect fuel injector 2, which is causing the 11-12 ohm readout, so that is probably normal. I couldn't get a good eye on 23-25, but according to the wiring diagram on Alldata (which has Porsche markings), 24-25 go to the starter and include the start lock relay. I'm unsure of pin 23. (Correction, Pin 23 is the Air Conditioning Relay, pin 87. So ~4 ohms is probably normal.) I think the X59 diagram provided by jumpy chunky has too many differences between the 99 and 02 motors.

Quotes source post: 20466132

So from this post above, is the following still true: PIn 4: < 1 Ohm to ground Pins 24 and 25: < 1 Ohm to ground Is that correct, meaning that all three pins are grounded? Or was it that 24 to 25 is less than 1 Ohm. Whichever pins are grounded to the engine, let me know the wire color (make sure you inspect closely if it has a strip on it).

Okay....I have the same large wire on my pin 4 but it is not grounded out.....let me look into this. Should be able to figure this out.

Quotes source post: 20468095

I got a good look. 4 - large black wire, 24,25- large yellow wires, no stripes. All have less than 1 ohm.

So looking at it, I believe it's most likely your power supply to the coil packs. The power comes in from C2 (not shown) and drops down vertically to the RED/WHT wire on pin number 3 of the Ignition/O2 sensor relay (on relay support 2). This is on the car side wiring of the X59 connector, so it's not the issue. Once the relay is picked up, it feeds the large black wire on Pin 4, go up and to the right to "33". It comes in on the right, travels to the left from 33 to 14, no connections on this diagram. It then comes across the X59 connector (the diagram doesn't show that connection) and is the power supply for all six coil packs. The negative side of the coil pack is feed to the DME and it provides a ground signal for each individual coil pack when it is needed. So your issue is a ground fault between that wire and ground. You can do a continuity test between X59 pin 4 and any coil pack wiring harness pin 3 and you should have less than 1 ohm. I would probably start here and verify that you have continuity on each coil pack. If one does not, maybe that is the problem child. If it all checks out, if you have a borescope, break it out and start inspecting the wiring for obvious issues, it comes in on bank 2, runs under the intake manifold over to bank 1 and drops down to the coil packs on each side. All the other wiring is in the same loom. Or if you can turn off all the lights in the garage or wait until the evening, have somebody cycle the ignition and see if you can observe a spark anywhere. Hopefully you can find it, if you need pictures of the wiring harness of the motor I have out, I can post them. If you are really stuck, feel free to PM me and maybe we can talk.

So here are some pictures of the harness for you. Comes in outboard of the AC compressor (removed in this picture) and goes through the black plastic tray with the tie wrap on it. Some of it goes off to bank 2 on the right, the rest goes under the manifold between the two ribbed plastic pipes in this picture. Here is bank 2, it comes off the back of the motor and goes forward, each of the coil packs come off the harness above the fuel rail. Here is the engine looking from the transmission back towards the engine, you can see it come from the top left about 10 o'clock, behind the oil cooler, across, over to bank 1. Then Bank 1 it comes in from the back of the motor near the transmission and routes over the fuel rail with the wiring dropping down for the coil packs.

I wish we had access to documentation on the manufacturing process of the 996, like the training on how to initially put the car together.

Looking at this some more, is there a possibility that the spark plug ground (brown wire, pin 2) could be grounded to the power supply? It does show GP10, that would most likely be the large ground cable going from the engine to the chassis at cylinder 6 near the coil pack. It would be worth a shot to unbolt it and see what you get for resistance on pin 4 of the large connector. Prior to that, you could just try measuring resistance from pin 2 to 3 at the coil pack connectors, normally that would be an open circuit, right now it should be a short based on your readings. I would measure it at all coil pack connections. I would also start a spreadsheet to take notes and document your testing. Or whatever might work for you.

Pausing for now. Out of town for the next couple days and waiting on parts. Still going to troubleshoot the issue, but I have multiple wires that I know need fixed.

One thing that you could do is to lift at least the ground connection for the spark plug circuitry, which is Pin 2 on the coil pack connection. There are two ground connections, one for bank 1 and another for bank 2. Here is the one for Bank 2, it would be just above the right hand side motor mount, it's three brown wires attached to the block with a 10mm bolt. This one is lifted right now, I get continuity from pin 2 to the lug, but it's not attached to the block, it breaks the circuit. So you could pull that bolt, lift the lug and then check Pin 4 of the large connector to ground. If it clears the ground, you're closer. Bank 1 ground point is on the back of the block just below the AOS, so not easy to get to. FYI, with the Bank 2 ground removed from the block as shown above, there is no continuity between the Bank 2 coil packs and the Bank 1 coil pack grounds. So at least you'll be able to split this circuit in two, considering you have a hard ground, this is in realm of possibility.

Quotes source post: 20470283

Got the engine out, figured I would have to anyways for any real wire repair/replacement. I measured pin 4 to the ground point on bank 2, open circuit. I also checked pin 4 to the variocams, injectors, coils and any other connector, including the main ground wire on the lower right. No contact except for pin 3 (I believe) on all coils and one pin on each injector. I did not record the color, but it was consistent. Open circuit to variocams from pin 4. The new (to me anyways) harness has arrived and I plan on replacing on Wednesday. I will be out of town tomorrow (Tuesday) but let me know of any other troubleshooting you would like to see.

Got the engine back in, but snagged the CPS (crank position sensor) wire on the way up, attempted to replace the CPS, but the sensor won't come out (I thought the bolt was going to be tough, but that was the easy part). Going to pull the engine again and separate the engine/transmission to get at it from the other side. Positive news, even with the CPS failure, after the new harness, no fuses popped!

Everything is put back together and there appears to be no issues. Word to the wise, pull the transmission before messing with the CPS, even going in it felt like a zero clearance fit and lining up the bolt hole was a task in itself. Not sure which wire(s) failed, but there were several with insulation issues. The parts cannon was the optimal fix this time. Thanks everyone for the help!

Well, we spoke too soon! Full throttle application, the engine cuts out at 5500 and if done too many times, will pop the CEL with P1266 and refuse to recognize throttle input until the car is restarted. Manual says to replace DME. I guess I'm going to give my PIWIS a workout. Maybe popping the fuses too many times damaged the DME, like @Paul Waterloo said.

More testing, I get P0335 and P0336 when I look at it with PIWIS. As long as I keep the car under 5k, there seems to be no issue, other than some occasional rough idle.

Quotes source post: 20485087

I'd check the connectors on CPS, clean and reseat fully. If no change try another CPS, make sure its fully seated and the correct one...

Quotes source post: 20485132

I triple checked the part number, but I�ll investigate the connector again.

Do you have a tune on the ECU? Are you in the US, and you're running the stock USA maps?

Quotes source post: 20485248

No tune, in the US (Georgia), and stock USA maps (although I would love to get RoW working to remove SAI and post-cat O2 sensors removed).

More testing. 70+ mile trip at varying rpm�s under 5k, no issue, appeared to have a steady reading. At a stop light, after approximately 1 minute idle, engine died and took two attempts to start. No CEL. At destination, was able to rev to redline for a moment, then the rpm was erratic, tach died briefly, and engine went to safe idle ignoring throttle input. CEL illuminated, but I haven�t checked the codes yet. I wonder if it is a bad CPS vs DME? Hopefully I can remove it without too much effort since I just put it in 100 miles ago.

More troubleshooting, some unsteadiness in the RPM readout on the 70 mile drive back. Engine did stop at one time. Same restart procedure. Checked PIWIS on return P0335 and P0336. Was able to rev to limit without issue when I tried again. I'm hoping this leans even more towards the sensor.

Quotes source post: 20486044

Hey, its worth a try to swap it out with a known good one. An inexpensive HT from Pelican has been in my car for almost 5 years now, working flawlessly... It might not be the mega expensive Porsche part, but it works fine, at least good enough to troubleshoot an intermittent bad cps... You said old one came out hard. Did new one also go in hard..? https://www.pelicanparts.com/More_In...T&KeepHeader=Y

Quotes source post: 20486166

The new one went in hard. It is the Bosch one from Autozone.

Quotes source post: 20486166

That doesn�t show as compatible for my 02 C2, but I am getting a URO one by Friday.

No start today, cleaned and reseated the electrical connector (the sensor had 0.88 KOhms as expected and the only thing easyish about this is the location) and appears to function normally. A few high RPM runs indicate no issues. Let's see how this plays out.

The loss in crank information at high engine speed still seems to return. Right now, it seems to be when the engine is warm. Attached is the most recent log from PIWIS isolated to just the P0335 and P0336. I did not get a CEL this time. I'd have to imagine its the sensor, any other tests to confirm its not the DME?

More testing, the issues seem to mostly pop up when the engine is warm/hot. I checked the resistance of the speed sensor at the X59 connector and it indicates ~1.0K Ohms, so that is within range for a good sensor. I'm going to check the resistance at the DME pins, but assuming the resistance checks out, I'm thinking the reluctance ring on the flywheel might be the culprit and does not allow a proper signal when heated up. I'm going to try and use an oscilloscope on the pins at the DME both hot and cold to check the "quality" of the speed signal. If there is a degradation with heat, I am assuming I need to replace the flywheel.

No oscilloscope testing required. I am geting repeated P0335 errors and coolant failure indicators (the coolant temp sensor is also new). I am pushing this towards DME replacement. The question is will the Online PT4G allow me to reprogram the new DME, as I don't think the clone PIWIS III has the required maps. I have PIWIS II as well, but not sure if it does either.

Contact ecudoctors in fl. They will do a health check for $99. They can also repair or replace as needed. I have used the twice and the communication is very good. I would also pull the dme plugs and use a 5x magnifier and look at the pins. My car had a bunch spred from a heavy handed tech that resulted in many random o2 issues.

I need a GIF for the "Jump To Conclusions" board from Office Space. While waiting to receive my K-TAG to clone the ECU (which I can't seem to get to work btw) I have driven it for a bit with varying degrees of unreliability. Yesterday, I ohmed out the CPS just to double check and after being warm from about a 30 minute drive (with some RPM irregularities and a stall at idle), the sensor measured ~1.3kOhms at the DME plug. I attributed this to being out of the range of 0.8 - 1.0 kOhms due to heat, but checked again this morning, being stone cold and it reads ~1.6kOhms. I guess I got a bad sensor from Auto Zone (even being Bosch branded and having the proper Porsche part number on it.) The part had the correct resistance prior to installation. The resistance measurements have been taken at both the X59 connector and the DME pins. When I go to replace it, I will check the resistance at the sensor first and see if it lines up.

This is the GEMINI analysis on your thread: Based on the diagnostic log and subsequent physical testing, the Porsche 996 is experiencing a critical failure of the Crankshaft Position Sensor (CPS), also known as the reference mark sensor. The engine control unit (DME) has recorded two primary active and static faults: P0335 (No Signal/Open Circuit) and P0336 (Signal Implausible). These errors occurred across a wide range of operating conditions, including a cold start at 25C and high-stress driving at 6440 1/min with engine temperatures reaching 99.75C. The frequency of these faults and the "static" storage state indicate that the DME can no longer reliably synchronize ignition and injection timing. Detailed electrical testing confirms a significant internal failure of the sensor's coil, even though it was a recently installed Bosch unit. While a healthy sensor should typically measure between 0.8 k$\Omega$ and 1.0 k$\Omega$, this unit's resistance climbed to ~1.3 k$\Omega$ when warm�causing RPM irregularities and stalling�and jumped to ~1.6 k$\Omega$ when "stone cold". This erratic resistance, documented both at the X59 connector and the DME pins, explains the "open circuit" and "signal implausible" descriptions found in the diagnostic report. The fact that the resistance remains out of spec while cold rules out external factors like the flywheel reluctance ring and confirms an internal manufacturing defect in the sensor. The definitive solution is a warranty replacement of the Crankshaft Position Sensor. Given that the current part was "Dead on Arrival" or suffered "infant mortality" despite being a brand-name component, the new unit must be bench-tested for proper resistance before installation. Additionally, the wiring harness and the 3-pin connector should be inspected for corrosion or damage, especially since the log recorded a low 1st-state supply voltage of 10.8 V. Replacing the faulty sensor and ensuring a clean electrical path will resolve the sync issues, clear the "Check Engine" light, and restore stable engine performance.

I recently read of another car with same issue that was chased for years and turned out to be a three fold problem...All related to corroded connections and high resistance under high loads.. The FIX ::: 1. rewire CPS circuit with dedicated circuit straight from CPS to DME.. 2. Clean and repair power leads to coils/injectors at X59 connector......( at warm temps and high RPMS the voltage would drop to coils/injectors and cause missfires/codes) 5. replace engine to chassis ground cable and clean connecting points, also add another ground cable from alternator to engine mount bolt... doing these may solve your problem as well ....

I like Porschtech's answer a lot better than Gemini's answer. AI thinks it knows everything.

Quotes source post: 20501560

Everybody agrees on that! Both do not focus on DME problem... I think the OP must follow ptech's advice...

You guys are probaly right. Part arrives today, then I will test the resistance at: The part connector The X59 connector The DME pins to make sure that it seems logical. Thanks again for all the help!

New URO part, checked resistance at sensor, X59, and DME. All good. Installed in car, seemed to work when on the jacks. Could go to redline with no issues. Took car out for a spin, still got stuttering and loss of tach when under heavy load. P0335 and P0336. Resistance after drive was about 1.1 kOhms, but the sensor was definitely hotter than 20 degrees C. Next stop, ground point above CPS (I did have to repair this on the donor harness) and engine to body. I have not checked the resistance on the shield pin to pin 32 on the DME III connector. Thoughts on DME?

Checked pin 32 against multiple other pins, no contact. Pin 32 to Pins 45 and 46 do produce about 7 MegaOhms each and that varies but is in the MegaOhm range, I'd imagine that's normal since they are all from the same sensor, but the shield does not contact ground anywhere I can find electrically.

Quotes source post: 20503111

So do the rewire of the cps sensor. Use an STP cable for automotive use. Ptech might be able to tell us what to use. For pins, 32,45 and 46. This is your next step.

Quotes source post: 20503219

Do we know what the resistance should be, if any, between the shield and 45/46?

Have you got the 8161 page long Service Manual for the 996? See page 7822-7823. The procedure to test is described there. A special tool is needed. The advice in turn is: Corrosion in the connector Open circuit or short circuit in the wiring harness Rpm/crankshaft position sensor faulty. DME control module faulty You have verifed (1) and (3), but not (2). Go for it. The resistance in the sensor should be 0.8�1.0 kΩ. Go for the rewire.

Quotes source post: 20503111

A little unclear as to the method used to check continuity. Id recommend disconnecting both connections for CPS. Check resistance between pin 32 at C connector on DME to pin A3 on connector should show no resistance. Dont check OHMs with C connector attached to DME. Pin 45 to pin A1= no resistance and pin 46 to pin A2 = no resistance. Both pin A2 and pin A3 go to ground at the DME only. Should be no continuity as far as I know between any leads incased in shielded cable, when cable is disconnected at both ends.

Quotes source post: 20504356

I was just checking from the DME side (unplugged of course) to determine if the shielding had any shorts between the other two leads in the sensor and also ground. The CPS was connected. Going back to the original issue, I had a constant fuse pop with the current wiring harness, replaced the harness after much troubleshooting and on the reinstall, damaged the original CPS. Installed a new one, but that one failed the resistance check shortly after driving. I'm fairly certain the wiring harness is good and the new CPS is good. My thought is that the DME was damaged due to the multiple attempts on troubleshooting the harness which caused the fuse too blow multiple times. The fuse has been stable since the wiring harness replacement, but I wonder if I am getting a failure on the DME due to the shorting. That is one of the remaining causes of the P0336 error code and the earlier P1266 code.

Okay, a bit of work, but I would disconnect the CPS from associated plug just to be sure all three leads are intact and not shorted one to another. Also a phenomenon I have experienced is that the quality sensors are usually found through dealerships. If the probe is difficult to remove and or replace I would take my brake cylinder hone and clean up the bore in bellhousing a little.

Oops engine block.

Short update. Replaced the DME with known working/good. Tested all temps and speed ranges (within limits). Appears to function normally, but I do get a little limiting at around 6500-7000 at high loads. 7300 no load is smooth as silk. The P0336 code will pop when it stutters under load. CPS replaced Engine Harness replaced DME replaced If I still need to run a new set of wires from CPS to DME, I would need some help on selecting the right parts.

Since you eliminated everything else, it is time for the cabling...

Quotes source post: 20508459

To anybody that has done it, what are the required materials and what is the best route? I plan on still leaving the original wires in place but want to take the most direct route to the DME.

Quotes source post: 20508634

Justin, if it were me, I'd quickly double check everything again. You said the cps came out hard and new one went in hard. I'd make sure the CPS mounting bore is clean, maybe take some sand cloth wrapped on a deep socket and clean/lightly sand its bore out enough so you don't have to force the new cps in. Grease oring and sensor bore, make sure it slides in nicely easily to the hilt before tightening down the bolt. If it is forced in and maybe not seated fully it could cause intermittent problems or even damage a new sensor... Only after doing the above would I go for the new/troubleshooting cps re-wire job. If it were me, I'd first do a quick wire job with easy not permanent troubleshooting routing, maybe thru the window and engine hatch just for testing before going thru a more time consuming permanent wire job. Maybe de-pin the dme cps wires from the plug and pin in your own set of wires directly routed to the cps connector using appropriate pins/connectors. Make sure to disconnect all existing wires. Use a 2 pair cable or even a 4 or 6 pair would be fine, maybe 16-20 gauge ? would be great for trouble shooting. Even some home t-stat wire would work fine for a fast trouble shooting job. Then give it a full long test to make sure before you go to the trouble of a neat, proper, permanent re-wire job, that this is 100% your problem... jmo

I would use an Ethernet STP cable, it has 4 pairs inside, each one with distinctive colors, use 3 single wires of them.

Quotes source post: 20509000

Ethernet cable I have plenty of. This project will have to suspend temporarily, as I am relocating to San Antonio from Middle Georgia, so moving takes precedence for now. It does appear driveable for the most part, just not high load, high rpm. I'll use this time to see if the signal degrades any further.

Quotes source post: 20510691

STP not UTP which is the typical Ethernet cable. You need this foil wrap to cover interference from injectors, spark plugs or other electrical components

Quotes source post: 20510695

I'm not sure what the gauge of wire is on the original cable. Do you happen to know the size of the connectors that slide into the DME harness at the DME III connector? EDIT: I think the connectors are correctly listed here: https://www.detmersdesign.com/blog/p...6tt-connectors They seem to be https://www.te.com/en/product-5-928999-1.html . (I just placed a sample order for 5, so we will see if they are correct). EDIT 2: Possibly 17ish AWG wire at the CPS connector. Allegedly, the Bosch 1928403966 is the equivalent part. Just need some sanity checking on that. The other question is, do all the wires need to be shielded, do the wires all need to be twisted, or can I just run the three bundled together to the DME? Maybe a slightly more in-depth look at how that portion of the wiring harness is constructed.

I would definitely twist the 3 wires, eliminate EMI and electrical noises.

It's been a hot minute. Between moving and getting settled here in Texas, there hasn't been much time for an update. Recap: Replaced CPS, Engine Harness, ECU/Immobilizer. Problem mostly went away. Have noticed the past day or so, that when it warms up, I am hitting a limit of about 5k RPM but produce no CEL (there was a pending P0335 code for the CPS). Cool engine, it seems to function normally. I have noticed that the voltage can drop lower then I would like when things turn on (around 12.2 ish and take a bit to return to around 13.8). I just replaced the engine to chassis ground cable on the right hand side and the voltage discrepancy seems to be resolved (hopefully it's not a placebo effect). The voltage appears steady at around 13.8, but when the A/C and/or cooling fans turn on, the voltage drops momentarily to midrange and then pops right back up. Headed to VCF Southwest (Vintage Computer Festival) in Dallas on Friday and going to shake it out with this drive. Wish me luck on the 4ish hours from San Antonio, and hopefully there are folks along the way if things go south (even though I will be heading north).

I know that everyone was waiting with baited breath on the progress of my journey. After 678 miles (mostly 80mph+, where legal of course :-)) there appears to be no issue. The full rev range seems usable at different engine loads and temperatures. There is some excessive noise from the A/C compressor, but that is scheduled to be replaced soon. There is a noticable bump or hesitation around 3k RPM, I have replaced the variocam solenoids, so not sure.