KarlNorth

My father is the original owner of his 2009 S5. Recently he did some maintenance work on it, took off the ECM cover, and didn't reinstall it correctly. Somehow water got into it and the ECM ended up getting damaged. He had it towed to a local Euro Specialist shop.

They diagnosed it and sent the ECM off for repair. Once the repaired ECM came back, the shop reinstalled it, but the car still didn't run.
The shop can't get a scan tool to communicate with the ECM.

One of the mechanics said the issue could be the adaptive motor mounts causing a short

They say the car needs a complete wiring harness replacement. This seems a bit over the top. I can understand if one or two of the wires were corroded or shorted by the ECM... but a whole replacement body wiring harness??

Any ideas?

Thanks folks!

-Karl N.

SMac770

All you can do is look at the wiring harness plugs to the ECM and see what the state of the pins looks like. The 94-pin and the 60-pin. Then check the 12v and ground lines on those plugs specifically, as well as the CAN bus lines. If the ECM is good, and the 12v lines and GND lines, and the CAN lines, then one would expect the ECM could boot and communicate. 12v are fuse 6 to pins 3/5/6 on T94, GND are pins 1/2/4 on T94. There's also 12v on fuse 4 to pin 92 on T94. There's also term 15 12v through fuse 3 to pin 87 on T94. The CAN lines are pins 68 (high) and 67 (low) on T94. So if 12v is good on the 12v to GND lines and the correct voltage activity is seen on the CAN high to low lines, seems it should comms ok.

The ECM grounds the motor mount lines to activate them. Is it blowing fuse 5 in the ECM box?