Hi,

I`ve been viewing forum posts for a while to try and figure out this problem but no luck.....

I can`t communicate with the ECU on my 99 A6 Avant with either on OBD-II reader or with VAG-COM. My Check Engine Light is always on and has been for about three years. Aside from this, everything on the car works, just can`t communicate with the ECU.

What is the most likely cause of this problem? Bad ECU? Bad Relay? Bad Fuse? Faulty Wiring? (if this is so, where is the most likely place that this could be?)

Based on what I`ve experienced and read so far, I don`t think it`s the ECU.
If you think otherwise, let me know.

Thanks