we have a 99 a4 1.8t it has a check engine light so we went to have it scanned and have no communication with the scanner, checked the usual fuses, wires,even read that wiring an aftermarket stereo may be the cause, if anyone has had the same problem please let us know how you fixed it........thanx

 

Did you figure out what was wrong, I just bought a 2000 s4 and am having the same trouble.

 

nope not yet.....will let you know when we do if you do the same.

 

I did some reading, looks like the "k-wire" goes from the OBD port through the stock radio and then into the ECU, I'm going to try and find the pin outs for the OBD connector and the ECU and just make a direct connection (next warm day), I'll let you know if that works. From what I've read, most of the problems we're having are due to a ripped / cut "k-wire"