2001 Audi A4 ECU - Short or Faulty

Tiny
SELLINGTHEWIND
  • MEMBER
  • 2001 AUDI A4
  • 2.8L
  • V6
  • AWD
  • MANUAL
  • 130,000 MILES
A few months ago I had parked my audi so that I could continue to work on it while not driving it daily. I put my 337 on the road and had unexpected bills.

As my car sat I would try to start it and let it run about every other day. I will give some background on the car.

2001 Audi A4 v6 Manual Trans

I had a few of the common Catalytic converter codes but when I went to scan it most recently after the battery had died, it had an ECM Fault code.

P0604 Internal Control Module Random Access Memory (RAM) Error

The car began to become hard to start.

The CEL would sometimes not illuminate with the KEY ON. Understanding there was something screwy with the ECM, I unplugged it and Plugged it back in. The CEL came on and I knew there was a good sign the car would start and it did.
I had continued this habit of unplugging the ECM just to get the car to start and run for a while. The time had finally come where I couldnt get the CEL to illuminate. I sent the ECU out to be repaired and they said the Processor was fried. Upon receiving the ecu, I installed it.
Without thinking I could do harm to this ecu, because I thought the issue was isolated to the ECU, I started the car. It ran for about 5 seconds and shut off. No CEL was displayed. The car would not start. I sent the ECU back out and they fixed it again for free but next time I would have to pay.(Understandably).

There are other issues that allowed me to drive the car for a solid year.
-Coolant Temp reading intermittent
-Oil Temp Intermittent
-Fuel Guage Inoperative
-ABS Light always on

-There is no coolant migration on the CTS plug.

-The Relay 373 on the side of the ECU clicks fine (75ohms)

I have since been out testing some grounds but need more information on what to look for. I asked the same questions on JustAsk. Com but they were vague in answering. Any help would be greatly appreciated

Thank you for any info. Peace
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Wednesday, September 9th, 2015 AT 4:18 PM

6 Replies

Tiny
RIVERMIKERAT
  • MEMBER
It looks and sounds like you've gotten a good start already. I can supply you with the engine performance schematics if that will help. From what you're describing, ground loops and faulty grounds is what I would be looking into, just like you are.
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Wednesday, September 9th, 2015 AT 7:37 PM
Tiny
SELLINGTHEWIND
  • MEMBER
Great! This is exactly the advice I am looking for. The grounds that I have checked so far are all.3-.5 ohms of resistance. I would love the schematics.

There are two multi-pin connectors that plug into the ECU. I do not have schematics but notice that VW/Audi use brown for a lot of Ground (so I tested them). On the larger connector both Brown wires are reading.2-.3 ohms and on the other connector the brown wire is OFL, or open. I am not sure I want to be assuming this is ground so a Diagram would be amazing. Thanks Peace
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Thursday, September 10th, 2015 AT 10:06 AM
Tiny
RIVERMIKERAT
  • MEMBER
Ok. This first really big one is everything we have on computer diagnostics.
http://www.dropbox.com/s/buis1x6gdr59cs0/content%3Dtabs%26module%3Dtrue%26.pdf?dl=0

This next one is the engine performance schematics showing everything.
http://www.dropbox.com/s/54duiv3znllf7v8/content%3Dtabs%26modu%3Dtrue%26.pdf?dl=0

Component locator table
http://www.dropbox.com/s/tpmzm3arkb26b2w/Components.pdf?dl=0

Component locator graphic
http://www.dropbox.com/s/ig2cs13rqkmjle4/Grounds.pdf?dl=0
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Thursday, September 10th, 2015 AT 12:53 PM
Tiny
RIVERMIKERAT
  • MEMBER
If you need anything else, let me know.
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Thursday, September 10th, 2015 AT 1:00 PM
Tiny
SELLINGTHEWIND
  • MEMBER
This is amazing. This is already the most help I have gotten in a while. I know my way around a multi meter and feel confident I can start asap.

I was recently speaking with the person that had charged my battery before starting it the second time. I guess the second time I had fried the ECM, the battery was charged to 13.5V. I know this should not have happened and I thought they would have known better and I should have checked.

Would this have done anything to harm the ECM the second time? I am just trying to rule out the possibility of chasing down a wiring problem when it was just a coincidence that it was an overcharged battery. I understand the vehicle can handle more than 14Volts, I just am unsure of this sensitive electrical system.

Thanks again. Peace
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Sunday, September 13th, 2015 AT 6:35 AM
Tiny
RIVERMIKERAT
  • MEMBER
It shouldn't. The alternator is supposed to charge at a constant 13.8 volts, so the battery being charged to 13.5 shouldn't be an issue. The only issue is if they hooked up the charger in reverse polarity with the battery in the car.
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Sunday, September 13th, 2015 AT 7:11 AM

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