ABY ECU Intermittent issue

[edge_devil]

Yes it is the check engine light then . The dashboard doesn't have room for the light hence the black box in the engine bay.


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[twoqu]

I was trying to determine whether its acting as a check engine light in effect.
So would illuminate with ign on and go out when engine started and if illuminated with engine running, that would indicate a fault.

GO PO!

[edge_devil]

Robin chips have arrived 👍 thanks.

Re the led, it is the diagnostic led as per http://www.sjmautotechnik.com/troubl...20v.html#outs4

I'll link up in a minute which pin it is, but I've only just got home... Gotta be nice to the missus see if I can go out and test the chips


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[twoqu]

Tim,
What ecu pin is the LED effectively connected to?

[UrS4boy]

The two way supply is a bit confusing. Wonder when the holding relay drops out of the loop. During cranking/running?

I agree on all counts, especially the confusing bit. It took me a long while to accept that power to those devices can come from two directions without issues. I eventually figured it out, no doubt with some input from Paul Nugent, reading what he had said about it. The secret is probably in the Holding Relay diagram that Paul N. did. Suffice it to say, the Holding Relay is involved before the engine is started and after the engine is stopped but very likely not while the engine is actually running.

[twoqu]

Think this is overlooked. Not only does it provide power to all the components prior to cranking/running but of course it allows the output tests which are conducted with just the ign on.
The two way supply is a bit confusing. Wonder when the holding relay drops out of the loop. During cranking/running?
Once the car is running it shouldn't have any input until its needed for the maf burn off after engine off.
Its a bit confusing looking at the schematics as power is fed out of pin 37 back up to the fuse box with ign on and then back down from the fuel pump relay when running!

[UrS4boy]

I was wondering why it says to check voltage with ign on at pin 37. This is to do with the holding relay. Rather than trying to explain, I suggest you take a look at Dave's explaination here:
http://forums.quattroworld.com/s4s6/msgs/102009.phtml

Thanks Robin for providing Tim with that link. The holding relay is one of the more important secrets of the ECU function. From that link:

"When testing to see if the Holding relay is working, when you turn the ignition on, there should be 12v power to the injector terminals connected to the black wire with the red stripe (probe the connector with only ONE mulimeter probe, ground the second multimeter probe to the cam cover)."

[twoqu]

I was wondering why it says to check voltage with ign on at pin 37. This is to do with the holding relay. Rather than trying to explain, I suggest you take a look at Dave's explaination here:

http://forums.quattroworld.com/s4s6/msgs/102009.phtml

[edge_devil]

Ineed Robin, thans again m8, I'm crossing my fingers that it's the ecu, although a pain at least the issue will be solved!

[twoqu]

So effectively erasing the code (by removing ecu power) allows the engine to run for 2 minutes before presumably the same code comes back. There does seem to be three variables. Ground or power issues and of course the unseen properties of the chips! Hopefully soon you can eliminate as least one of those!

[edge_devil]

I unplugged it afterwards and made another video I haven't posted and she ran fine.....then stopped again after two minutes. My gut feeling is a dirty/dry join in a cable or an unseen ecu issue.

I'm trying to have to avoid taking the body off, it's a 4 hour two man job, but if I have to I will and then go through all of the loom piece by piece again..... Sigh....

I do really appreciate the support in this forum, it's just a frustrating issue!


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[twoqu]

I am wondering if the clanging of the ISV means its in limp home mode due to the seriousness of that code. Its a grey area what happens in limp home but one documented occurance is that the idle speed is raised to 1100/1200 which can only be achieved by full stop activation of the ISV.
Nothing to lose. Temporarily power down the ecu and then reconnect and try. If the code comes back we will at least know it a current one!

[edge_devil]

The FP relay outputs seem to be the same, so I'm risking that as okay. Re the fault codes I need to read up on what's involved etc etc and the I'll make the loom and get the software and start reading it all out. I haven't got the original diag pins, two were on the loom one was gone but I can re create it by opening my black box with the led and adding an extra loom plug for diag.


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[twoqu]

Just two quick observations.
The first is that the fuel pump relay looks likes it off a 10V not a 20V as it has the fuse provision in the top to iniate fault diagnosis. Can't remember if they are the same from a contact point of view. If so ignore!
Second any faults codes will be stored by the ecu until they are erased. Thats relatively easy with VCDS/Vagcom. The only other way is to remove the 12V permanent power supply to the ecu for say a minute of two.
Just wondering if you are chasing a ghost fault code in effect. Obviously if you erase a code and it comes back then its an issue.

[edge_devil]

Just a quick video so you can understand the nature of the issue. I switched on the ignition after checking the gnd and 12 pins, & this is what happens when it's playing up...

http://youtu.be/7sz0eJJ7ulg

The clicking is from the ISV btw.

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