Hi, I have a 1995 GTI 8v, with an interesting fault....
The OBD is throwing up a very occasional immobiliser fault whilst driving, which cuts the engine. I have initially traced it to either the ECU, or the immobiliser unit. All wiring and relay operation is fine - however, as an experiment I have noticed that when the engine is running and I disconnect the immobiliser unit (either power supply plug or key/coil sensor plug),there is no affect, the engine keeps running - only when you turn off and try to re-start will it recognise there is a problem; this leads me to think the immobiliser is doing its job, sending the correct signal to the ECU on start up, and for some reason the ECU is developing a fault which it resets/interprets as an immobiliser problem, and then forces shut-down.
Does any one have experience of the protocol between the two units i.e. the type of signal/timing that the ECU is looking for from the immobiliser unit? Any findings from a similar investigation would be appreciated,
Alternatively, has anyone got a cheap siemens ECU, or one I can borrow to confirm or eliminate the ECU? I am located in Portsmouth area
I'm reluctant to just swap out the ECU/immobiliser/coil/chip/key for the sake of it without understanding the cause of the problem!
Otherwise it could be a cheap project for someone, would prefer the space for one with more valves and less doors!
Thanks