2005 VW Golf GTI 2.0 TFSI Won't Start - Fault Codes P0688, P2149, P2146, P1602 (P2146 Repeated)

Model: 2005 VW GOLF GTI 2.0 TFSI Fault Code: P0688 Posted: 2019-04-22 15:38

My 2005 VW Golf GTI 2.0 TFSI engine cranks but will not start. After accidentally connecting the positive and negative terminals during maintenance, the vehicle failed to start. I have checked all relays and fuses, which are functioning properly. However, the voltage on fuse F6 (Engine Management) is only between 3.4V and 4.5V, significantly below the expected level. The onboard diagnostic system shows fault codes P0680, P2149, P2146, and P1602, with P2146 appearing twice. I am concerned whether my ECU has been damaged or if there is a wiring issue causing these faults. Please advise on next steps for diagnosis and repair.