2000 S4 Avant stalls, Vag Com won't read Engine or Instrument modules.

[Blau_RS2]

I was getting a code for my EGT Sensor in the bank 2 postion so I opened the sensor up and tried re-soldering the connections before throwing money at it.

I plugged everything back in and the car started right up, however all the lights in my heater controls were flickering like a christmas tree. I stopped the car and checked my work and realized I left a ground wire off one of the screws that hold the EGT sensor to the block. I tightened that up and tried to start the car and it now keeps stalling.

It seems to run for about a half second and then shuts down. At first I thought it seemed like the immobilizer kicking in but the immobolizer light comes on when I turn the key and then shuts off to indicate it has made a connection with the key. It is definitely not just turning over. If I hop on the throttle quickly I can rev it but it still stalls out.

Here's the Vag Com details.

- Everything worked fine before I tried fixing the sensor.
- After the car would not start I tried the Vag Com again and received an error saying there was no response from the controller and I couldn't read any modules.
- I pulled the plug on the bad EGT and then I was able to access all the modules except the 01 Engine and 17 Instruments.
- Tried pulling the ECU, same results.
- Tried disconnecting the Instrument cluster, same results.

I pulled all fuses and found nothing blown.

Does anybody have any suggestions I could try?? Not sure what else I can do other than swap ECU's. Problem is it's a D Box from Europe. I believe I've got the immobolizer 2 which doesn't affect the ECU so an A Box should work from what I understand.

Thanks for reading.

Dave

[Calif_Kid]

I recently watched a YouTube video of someone troubleshooting a no start issue on a minivan. When they tried to check for OBD-II codes, the OBD checker would not connect. With the key on, they then checked some sensors under the hood that should have 5V, and found them reading low voltage - say 1.7V. They then checked at the ECU for ground and 5V, and ended up figuring out that there was a short in a power wire leading to one of the sensors. The main point I'm trying to make, is that if there is a partial short, and it is dragging the voltage low, that it could cause the scanner not to be able to connect. I know that Vag.com isn't OBD-II, but just wanted to mention the info. - Jim

[Blau_RS2]

Could a bad ground fry the ECU and prevent the vag com from communicating with it and the instrument module?

[zillarob]

Looks like 12v, signal, and sig ground maybe?
If you got 12v to the sig or sig ground, could cause probs. Open the egt and ecu up and see if it looks like the smoke got out.

The heater lights should be a totally separate circuit from the ecu so I cant see how they would be affected in relation to your ecu prob.
Might read up on if the immo locks you out of the ecu/cluster if it thinks it is being tampered with?