Audi A3 in the workshop this week with every dash board warning light on the dash . After speaking with the customer we established that this was a sudden occurrence with no real clues as to why. Initial investigation and a global scan of the vehicle soon gave us a clue as just about every control unit had a no commination fault with the ABS control unit .
The plan was to start as always with basic checks all fuses were tested and found to be intact so were removed the ABS control unit plug and after consulting wiring diagram’s we tested voltage feeds and grounds at the main connector and found a main voltage feed missing .
Tracing the wiring back we noticed that the main harness which runs behind the battery box had been chaffing and there was a nice green stain on the outside of the insulation a sure sign of corrosion and water ingress .
When we opened up the wiring loom we found a completely corroded wire and a continuity test revealed this was our culprit . After cutting out the damaged section and soldering in a new wire we reinstated the ABS connector and we then able to communicate with the ABS control and all previous faults cleared and all dash lights were now out.
After relearning the steering angle sensor and an extended road test we could confirm that this car was fixed without any major control units required .