Question for all the smart folks out there...

We have a 1998 A6 that will not turn over when the ignition switch is rotated to 'start'.

Troubleshooting reveals the following:

- When key is turned to 'start', +12v is at pins 2 and 4 of the starter interlock relay (J207)
- The relay bench tests fine: when +12v is applied to pin 4 and gnd to pin 6, the relay closes and continuity is made between pins 2 and 8

additionally, when pins 2 and 8 are jumpered with the relay is removed, and the switch is rotated to 'start' the starter operates (turns the engine over). Also, with the relay installed and the cover removed, the contacts manually closed (with the switch rotated to 'start') the starter operates.

I've concluded the relay and basic circuit is fine.

The suspect is this and would like anyone's opinion/help:

Pin 6 is the ground circuit to operate the relay which gos to the central locking system where, I assume, the module applies the gound to 'sink' the voltage, thus operating the relay and starter.

Any clue as to how the central locking system accomplishes this? All other aspects of the locking system appear to operate correctly (e.g. door locks, trunk, key fob as well as other interealted systems - windows for example)

Thanks in advance for any help!

 

As far as I know, the central locking system reads the key code and decides whether to ground the relay or not. A defective module would cause your car to no-start. Additionally, a defective key code reader would also cause a no-start condition. Are any codes showing up? It seems to me you should be able to monitor the system with a VAG-COM and see what is going on, although it may not give you the defective part. A bad key chip will also cause a no-start. Most of these problems require a trip to the dealer.

When you jumpered the relay, did the engine start? Not just turn over, but fire up and start? I may be wrong but the central locking should also kill the ignition. So, if you had a bad module or reader, the car would turn over but not start. Something to look for.

Good luck,

Bob

 

Bob,

Thanks for the reply. I should have mentioned that the car will start right up and run fine; I have a generic OBD II Code reader and there are no fault codes detected.

That said, I feel you're on to something Bob. While the 1998 doesn't have an immobilizer as determined by the instrument cluster design and part number ( analog clock and '00' in the last digits of the P/N), I strongly feel it's a key code issue, however I really don't have a clue how to validate the key or determine if the central locking system is recognizing the key. If, in fact this year car actually does such things...

- Martin