VW Passat Hybrid Starting Failure: Relay vs Solenoid Fix

Had the exact same symptoms on a 2016 VW Golf GTE Hybrid at 70000km. Car would not start and displayed similar error codes. After thorough diagnostics, the issue was traced to corroded battery terminals and a damaged wiring harness near the starter motor. The voltage drop was significant when testing the circuit, indicating poor electrical flow through the ignition switch system. The starter solenoid was actually fine, but could not receive proper current due to the deteriorated connections. The repair required: Complete cleaning of battery terminals, Replacement of the main wiring harness section, Testing of all ground connections, Reprogramming of the starter circuit module This was classified as a serious electrical system issue that could have led to complete system failure if left unaddressed. The car would have eventually failed to start completely. When visiting the workshop, request specific testing of: Battery terminal connections, Voltage readings across the ignition circuit, Wiring harness condition near the starter, Ground strap integrity Good to bring these points to their attention as they might save diagnostic time by checking these common failure points first.

Thanks for the detailed insight. Dealing with same starting issue on my Passat too. The wiring harness deterioration you mentioned makes sense, especially since I noticed some intermittent electrical problems before the complete failure. Before heading to the shop, checked the fuse box and battery connections myself but found nothing obvious. Did any other electrical issues pop up after your repair was done? Also curious about the final repair cost, would help me budget for what might be coming.

Thanks for asking about the follow-up. After getting the repair done, the starting issue was completely resolved. The mechanic identified Terminal 15 ignition positive interruption as the core problem, which matched the symptoms we both experienced. The faulty connection at the ignition switch was causing the intermittent power supply issues. Since the fix, no other electrical problems have surfaced. The repair bill came to 95€, which covered the cable replacement and resolving the connection issue. The fuse box and starter solenoid were thoroughly checked but found to be working correctly, it really was just that one compromised connection causing all the trouble. For your Passat, definitely have them check the Terminal 15 circuit specifically. The relay switch and related components in this area seem prone to connection issues in these models. Getting this sorted early prevents more extensive electrical system problems down the line.

Thanks for the input. Finally got my Passat fixed last week and wanted to share the outcome. Turned out the voltage drop was indeed caused by a deteriorating wiring harness, but also found a failing circuit break that was interrupting power to the starter. Took it to a new workshop that specializes in VW electrical systems. They immediately spotted the issue after testing the ignition switch connections. Total repair came to 780€, more than expected but included replacing the complete harness section and installing a new circuit protection system. No starting problems since then and those unusual electrical glitches are gone too. The fuse box and battery terminal connections all checked out fine, just as I thought from my initial inspection. Really glad I got a second opinion and proper diagnosis this time. For others facing similar issues, definitely worth finding a shop that knows these hybrid systems well. The first mechanic missed these failing components entirely.