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Spare remote key doesn't start car - why?


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With regards to a 1999 996 C2...

This morning my wife "inadvertantly" took my keys to work with her. I grabbed my spare remote key, and to my surprise the dash would light up, but the car would not start. So I grabbed the valet key, and the car started. Just curious as to why this is the case. The battery was good in the remote key. What is the reason for this? I am sure it's related to anti-theft, but don't understand it.

On a possibly related note, both key fobs stopped opening the doors probably 2 years ago, so I have been using the door lock since that time, but have only been using one key for that period. I have tried all the described methods for re-mating the keys to the anti-theft module with no dice. So I just decided to live with it, vice spending $100s to get new keys or key heads.

Please enlighten me...thanks.

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In the non-working key, I am guessing either the transponder pill has gone bad or is not "mated" to the immobilizer any longer (or never was).

Have you confirmed this by transfering the pill from the working valet key to the other non-working key?

And have you checked/replaced the battery on the remotes regarding their inability to unlock the doors remotely?

Edited by logray
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In the non-working key, I am guessing either the transponder pill has gone bad or is not "mated" to the immobilizer any longer (or never was).

Have you confirmed this by transfering the pill from the working valet key to the other non-working key?

And have you checked/replaced the battery on the remotes regarding their inability to unlock the doors remotely?

I have not confirmed that the transponder is bad, by swapping it out, but more than likely that's what it is. Was in a rush this morning. I was informed (by a friend) that the valet key likely has a chip in it that allows it to start the car. Still confused how a non-powered chip works fine (in the valet key), but a "powered" chip has decided to fail (theoretically it should work with out power if the valet does). Perhaps it isn't that its failed, just that it isn't mated to the car (being that it can be re-programmed, but a valet key cannot be reprogrammed.) Perhaps I reprogrammed it to my neighbors car...sweet, will look into that this evening. Will swap the guts of the keys this evening to confirm a bad transponder (or one that needs to be reprogrammed).

In regards to the inability of the remotes to unlock the doors, yes I did try swapping out the batteries, then the various methods of reprogramming them to the immobilizer/alarm system (i.e. unlocking doors, key in ignition, holding button for a couple seconds etc) I also replaced the battery in the non-working key again this morning.

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IIRC, the transponder pill does not need power, similar to passive RFID (it might even be passive RFID). This is why it works in your "non-powered" valet key.

The tranponder pill receives the RF request from the immobilizer, when close enough to the ignition switch, and then uses that energy to respond with the correct code, and if it matches to the immobilizer, enables fuel and spark.

Transponders and remotes cannot be re-programmed unless they are accompanied by their 20 digit programming code (typically on a piece of paper printed along with a new remote), and this also requires a PST2 or PIWIS programming computer in order to program. There is not a sequence of pressing buttons I am aware of that will "mate" the FOB to the immobilizer.

Edited by logray
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Question on the transponder pill., I got a new (Porsche design key) for my 996, both the new key and my old one's have the tip of the copper pill pointing AWAY from the key., however the instructions on Suncoast's site have a "note" that it must point towards the key., so I'm confused as my old keys obviously worked?! Which way is correct, or does it not matter as it's close enough to they ignition?

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Question on the transponder pill., I got a new (Porsche design key) for my 996, both the new key and my old one's have the tip of the copper pill pointing AWAY from the key., however the instructions on Suncoast's site have a "note" that it must point towards the key., so I'm confused as my old keys obviously worked?! Which way is correct, or does it not matter as it's close enough to they ignition?

You posted this same response/question 3 times - please re-read the board Guidelines/Rules that you agreed to when you registered here.

"Please post your messages in one forum only. Crossposting, double posting, triple posting, etc. are all a waste of time and valuable resources. If you post the same message in multiple times or in multiple forums, we will delete the ones we feel are inappropriate."

Your additional posts have been removed.

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Sorry about that., I wasn't aware of the rules against multiple posts (as i logged in via Facebook) and was just trying to get an answer from different / multiple participants. If anyone has an answer to my question I'd appreciate the help (and promise to follow the rules going forward)!

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From what I read on RFID, I suppose it's close enough facing either way. I'm just wondering why some write up's I've seen have the coil facing towards the key (which agrees with the work procedure 96.62.31.40) but my old keys and new design key have the coil away from the key.

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