Hi all -- I hope you can help as my 99 A4 Coupe has been giving me major electrical issues. Here's the rundown:

Problems:
• Service Vehicle Soon Message on DIC, all the time. If I clear codes it comes right back.
• TC and ABS lights on dash
• Steering is Heavy 90% of the time (PS obviously not working)
• Climate Control Panel Dead (not dim, dead. Lighting does come on with the headlights, though)
• Reverse Lights not working

The battery is about 1 year old. It went completely dead over the winter but was recharged, out of the car, and now seems to hold a charge fine. I had it tested at Advance Auto and they said it tested "good", to.

Odd behaviors:
For a while the Service Vehicle Soon/TC/ABS messages would go off when the car was shifted into reverse. At the same instant the Climate Control Panel would come on. It hasn't done that in the last 20 or so times I've tried it, though

Very occasionally the lights/messages/heavy steering would disappear after driving the car for 10 minutes or so. Hasn't happened lately.

Codes:
I took the battery out of the car and charged it overnight. I put it back in and got these codes:

10-PCM P1571 H C (Traction Control Torque Request Circuit)
10-PCM P1689 H C (Traction Control Delivered Torque Output Circuit)
28-TCS NO COMM
40-BCM B0432 HC (Rear Defogger Relay Circuit)
58-SDM U1040 H C (loss of communication with tcs)
60-IPC NO CODES
80-RADIO NO COMM (I have an aftermarket HU and amp)
99-HVAC NO COMM
AO-LDCM NO CODES
A1-RDCM NO CODES
A6-SCM NO CODES
BO-RFA NO CODES

So far I've:
• checked all the fuses in both boxes
• replaced the #38 Relay in the Engine Compartment fuse box
• cleaned the grounds on the frame rails in the engine compartment
• Added a second 4 gauge ground from the battery to the frame
• Verified that the reverse lights flash with fob locking (they do)
• Screamed, yelled and cried

Nothing seems to be working. I'm wondering if it's two separate issues since the codes point to the TCS system but the reverse lights/climate control issues seem unrelated. I'm thinking that my next, more involved step might be to replace the ignition switch as my searching indicates that some people with some similar issues did that and had some success. Or is there a reverse/backup switch somewhere on A4s that might be causing the issues? I'm hesitant to just start replacing parts until I at least ask for the wisdom and insight from the awesome CF veterans.

Any ideas would be HUGELY appreciated.



Thanks in advance.
Rich

 

Thanks, I'll have a look at that door connector next.

 

Hi all -- just wanted to update this thread to say that replacing the ignition switch fixed ALL the problems. I took the old one apart and sure enough, several of the contacts had black/burn marks on them.

The car only has 56k on it, btw.

 

It fixed the climate control panel!? And the power steering pump?!!

 

Yup. My guess is the computer just wasn't getting activated and thus shut down all the systems that it controls.

 

You have to remember,,,, The ignition switch supplies most of the modules with a seperate 12 VDC input. (HOT IN ON AND START) If that voltage is not there or low out of spec,,, the car is not going to function correctly. The NO COMMS on all those modules was a prime give away that you either had a voltage issue OR a Class II Serial Buss issue

Proper troubleshooting would dictate that you check the HOT IN ON AND START fuses for the module that have NO COMMS and see if that voltage is correct.

 

Thanks Bill. I ran the codes again and I'm no longer getting any "no comm" issues... all the codes were historical and haven't come back.

I AM still getting persistent Pull Key/Service Column Lock messages, but I suspect that's a secondary issue. I think my next step will be to check the pass floor relay -- unless you have any other suggestions?

 

Check the relay but,,,if you dont have the CLB,,, GET IT SOOOOON!