Engine stalling, ABS light flashing, Rev' counter not working, A.C. fan stopping!

[British-Audifan]

Hello folks, I'm in need of some help with my son's A4 which has started doing some strange things over the passed week!

Location, Gilbert Arizona (so hot!), The car:- 1998 2.8 30v, FWD Auto Avant.

The problem:- It has started breaking down while he is out and about, so I have stopped him driving it. The engine cuts out, but at the same time power to the a.c. fan seems to go as well, along with the aux fan on the condenser/radiator. The rev' counter stops working and the ABS light comes on with 3 beeps. If you crank the car it will start up again, but takes a bit of time to do so. Sometimes the rev counter will stop working and the ABS light will come on, but the a.c. and engine continue to work... for a while.
So it would appear to me that some major power source is being lost or turned off!? I thought perhaps the ECU might be at fault? Or it's loosing power? So I removed the plastic cover to get to the ECU, and that this is bloody hot!! I can hardly touch the thing. Should these ECU's get that hot? It cools down if you turn the car off..
The problem does seem heat related, 'cos, if we leave it in the garage overnight, and take it out into the heat, it will run for longer, then if it's parked outside for 3/4 hours!
I'm not getting any ECL's either...

I don't have VAGcom, but I have a hand held scanner, which when plugged into the OBDII port loses coms with the ECU when the engine stalls! But the power/ignition is still on!?

Does this sound like a ECU (ECM) issue? Or do I have a power line dropping out somewhere? Perhaps a relay supplying power to the ECU? But which relay? And where would that little bastard live within the car .

And the other problem is my 17 year old son is now driving around in my 4.2 V8 C5!! And enjoying it a bit too much!!

Any ideas?? Anyone else ever seen this problem?? Any help or suggestions would be wonderful..

Thanks guys,

Paul

[Mad Cow]

The ECU definitely shouldn't be getting that hot, it shouldn't even be heating up in any way apart from outside forces like engine bay heat. I would open it up and see if anything looks burnt, but in any case it's most likely gone bad so I'd be on the lookout for a new one.

[British-Audifan]

The ECU definitely shouldn't be getting that hot, it shouldn't even be heating up in any way apart from outside forces like engine bay heat. I would open it up and see if anything looks burnt, but in any case it's most likely gone bad so I'd be on the lookout for a new one.

Thanks for the reply. I did in fact open up the ECM, and nothing looks out of place! I did run the car for a while with the case off the ECM, just long enough to measure to temp of the chips on the board, and they went up to 150/160 degrees F pretty quickly! But the PCB seems to use the metal case as a heat-sink, so put it back together. Very strange issue. However it did throw a code, P1602, lose of rail 30, 12 volt power. I haven't removed the battery, so I'm loosing power to the ECM, or the ECM is faulty. Back out into a very hot garage for more checking....

[British-Audifan]

I thought I would post an update on this issue, just in case some other poor bastard like me, has the same issues!!

After much signal tracing etc, I found the ABS control module was dragging down the voltage supplied to the instrument cluster! Which seems to control many things!

So with the ABS module unplugged, the car ran without issues for days! So sent the ABS module out for repair and re-installed it, and now all is good! Just thought I would

share the fix...

Cheers,

Paul