Ok i have a 2000 Audi A4 1.8T manual FWD with about 80,000 miles on it. I am trying to fix a problem that happened after i made a huge mistake and reversed the jumper cables while i was trying to jump start it after it had been sitting for a while. Ok so once i turn the key on i don't have a check engine light or ecs light at all. I tried to check codes but it is not communicating with the engine module. All other modules check out fine but i can't get anything off the engine module. The engine itself will turn over but not fire. I have tried checking all the fuses and replacing the ECU relay and the ECU itself and neither of these fixed the problem. I am thinking the wiring harness but i wanted to know if anyone knew of a certain area to look at first. Thanks for looking.