Not the average key fob isn't working thread

Hi all, New member, blah, blah, just purchased an '03 C4S several weeks back. Hopelessly falling for the car... Anyway, like many others, my key fobs are not unlocking the car. A few details that are interesting: -New batteries in fobs, the LEDs light up -Car starts fine but alarm does go off if I unlock the door with the key and fail to put the key in the ignition within 10 or so seconds (pretty hilarious) -In car LED blinks when locked -I've tried every iteration of the wake up procedure -I reflowed the solder on the PCBA already Here's the big twist: I confirmed that my key fobs are transmitting. It just so happens that I work in the auto industry for a supplier with intimate knowledge of the keys. One of our engineers was kind enough to test them for me, and they both transmit. He even pulled the original wiring diagram to confirm what he saw. All that said, how on earth do I troubleshoot the receiver for the signal? It does not appear to be a sub module within the immobilizer, rather, is this embedded in the body controller? Any help is greatly appreciated, this is maddening! Still love the car though.

Have you tried taken the car to your local Porsche service center to have the keyfobs "mated" to the car's immobilizer/security modules?

Be close to the car when you click. The range is 4'. There is a way to up the range to 30'.

Ah, I have not. Our engineers knew the hardware well, but Porsche did the programming originally. They did mention that the system looked like it used a master key type system...that at least one of the keys needed to transmit the correct data in order for the system to unlock for programming period. I'll try the dealer next unless anyone else may have a DIY diagnosis procedure.

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^ This. Realistically this is the only way. Sucks to have to go to the dealer for this, but remember the key and security system work together to prevent the car from being stolen. Make an appointment and take both keys.

As many "keyfob/immobilizer" threads have appeared in the most recent past, in most cases, the only way to rectify these types of keyfob problems is to take it to Porsche and they have to connect it to their system for re-programming. There was one guy here on Rennlist that could reprogram the immobilizer modules, but he hasn't chimed in for more than a year. Kind of a programmer type of guy.

Such a bummer, but thank you all for the help. I'll post here after I try that.

Even a dealer may not be able to reprogram keys without the bar code for the key

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I believe the VIN will give them the info they need.

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Nope. Vin just gets the key learn code to access alarm module with tester- you will still need the 16 character code that comes on the barcode tag with every new fob. Without this number the dealer can do nothing but program new remotes or reteach the pill/immobilizer portion of the key. It will start it and shut off alarm in the ign switch, but still no remote function. perhaps if your technical guys can pull this Fob specific code from the data transmission a dealer could attempt it- but I'm quite positive a transmitted security code like that would be encrypted in some way so you couldn't clone your neighbors remote

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Wow...very complex. Wonder how many folks still have (or ever received) the barcode tag - I know I've never seen such a tag.

When you buy a new fob, it should have the barcode tag I don't believe that will come on a key delivered with the car

So if I live on an island with no P dealer I'm SOL?

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:IF: you have a barcode tag :AND: there is an independent service place that has a PWIS or PST2 :AND: they have good contacts at a Porsche dealer that will get them the security codes :THEN: you might be able to get a key programmed to your car. So basically, you are SOL

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The code is encrypted according to the engineers. Additionally, they didn't know much about the body controller (supplied elsewhere). So much for a free fix!

This is a Porsche we're talking about, nothing is free! Good luck with the dealer...

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Can you share details on how to achieve this range upgrade? Thanks!

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I just posted this last week, works great. https://rennlist.com/forums/996-foru...ttle-time.html

Quirky alarm/central locking issues can occur if there has been any moisture in the immobilizer box, located under the driver's seat. If you have a cabriolet and your drain plugs are clogged (common) or your car got rained on with the top down at some point in it's life, your floorboard could have gotten wet enough to let water get into the immobilizer. All it takes is a really hard rain and a little bit of moisture to get into the box. A soaked immobilizer and you could end up with immediate failure, but just a little bit of moisture can fester and you get gradual quirky little issues that start to crop up over time. The symptoms of immobilizer damage I experienced included intermittent no-start of car, windows rolling down on their own from time to time when parked, passenger door wouldn't lock when using the dash door lock or remote or key, remote didn't work for either door. Basically, I had failure of the central locking system as a whole... When I opened up the immobilizer I found roughly 1/4 of the circuit board had evidence of old water corrosion. New immobilizer, keys and programming = $1500 dealership experience. Best of luck to you, I hope you figure it out and it's not your immobilizer. If you do end up having an immobilizer problem, check out www.ecudoctors.com . they may be able to repair/rebuild yours and save you some money.

Key with code attached. If a PO had to have a new key programmmed they might have stuck the tag in the manual for future reprogramming. https://www.google.com/search?q=pors...W1m-GGeKGtTYM:

While you have probably done this, I don't see it in the thread. There are several conditions that can cause the receiver to turn off. If the car sits unopened for 5 consecutive days or if the receiver receives 256 "bad" transmits before it receives a good one (one of the reasons for the short receive range). The way to clear that is to insert the key into the door cylinder and turn to the left to unlock the car. Then press the remote button which will re-lock the car, if all is working, then remove the key. Basically it has to see the RFD chip of a known key before it will respond to a transmit. Good key with no transmit does not turn the receiver back on and a good key transmitting without being in the cylinder does not work. Like I said, you probably tried this but thought I would mention it anyway.

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Thanks for that...I can see where the purchaser of a new key would have the bar code but did the bar code come with the original keys and where do we find that info?

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I've tried a few permutations of that. To confirm, and this sounds silly, you do this with the door closed and locked to begin? I've tried that repeatedly with no luck with either key. The windows drop nicely however.

Yes you do. I've never tried it with the key out of the cylinder so that might work as well but the key (pun intended) is that the immobilizer needs to see a recognized key RFID, and possibly the physical key that maps in its memory to the key code being transmitted. The receiver actually turns off after 5 days to reduce battery drain or after 256 unsuccessful transmits to avoid a "sweeper" scan attack. When you put the key in the lock it looks up the RFID in its memory and allows you entry. It also temporarily reactivates the receiver but not for long. If it receives an alarm signal from a transmitter that is associated with that particular RFID, it restarts the receiver. I have heard of the memory being corrupted somehow and losing its coding, most common is water in the immobilizer. It sounds like your immobilizer is working correctly but either the receiver is damaged, like you surmise, or the key fob on the key is not associated with that RFID either through damage to the immobilizer or a changed fob. As pointed out at that point the only fix is for Porsche or someone else with the correct gear to reprogram the immobilizer and it needs the bar code from the key fob. Has it ever worked? Is there a chance that the key fobs got reversed somehow? It has to be the right key fob with the right RFID not just ones the car knows. Since the RFID pill is physically inside the fob, that is usually not a problem but maybe someone tried to recondition the fobs, had them both apart and put the wrong RFID pill in the wrong fob. Far fetched but...