GolfGTIforum.co.uk
Model specific boards => Golf mk3 => Topic started by: jonno74 on 06 September 2011, 18:45
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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
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Relay number 30 is on it's way out :laugh:
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http://www.golfgtiforum.co.uk/index.php?topic=140971.msg1283951#msg1283951
http://www.golfgtiforum.co.uk/index.php?topic=27880.msg224051#msg224051
http://www.golfgtiforum.co.uk/index.php?topic=197597.msg1839124#msg1839124
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thanks for the info! much appreciated ... so in your case, the ECU relay (30) was causing the system to report an immobiliser fault on the OBD scan?
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Yes it was,guy i bought car off threw money at mechanics who tried everything but car got steadily worse up to a point where it would just fire and die.
If you look at the last link in the 3 i gave you can see what i mean.
It could obvioulsly be other things but the symptoms you give sound the same as mine.It's your cheapest option,new relay was under £17 from VW dealer.If you are close to a breakers,even cheaper !.
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ok thanks, yes I've read your thread, great info, i'll give it a try! I did try bypassing the main switch contacts of the relay, with no change to the fault, but without a detailed schematic i don't know the interaction of the other pins (86,86a,85).
Ordered new relay from euro car parts , £11 free delivery, will let you know how it goes!
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Its not the relay! pinned it down to the ECU, it appears to have an internal fault, which with a bit of encouragement can be induced at will (i.e a big thump)! .
Just need to find one before Cadwell Park on Tuesday!!
has anyone got a 037 906 025 H ECU available in the Hampshire area?
cheers,
Jon
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You will need matching key as well with the chip in it.
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hi, I read that the the immobiliser box is coded to the key, not the ecu?