Scirocco Won't Start After Mechanic Shop Visit

Had a similar situation with my Golf 2.0 TDI (2014). After investigating further, the issue came down to a loose battery terminal connection that occurred during routine maintenance. The voltage drop was significant enough to trigger fault codes while still allowing the starter motor to crank. The wiring harness typically connects to several critical components through the fuse box and multiple circuit break points. In your case, since the problem started after mechanic work, check these basic connections first: 1. Battery terminals for proper tightness and corrosion 2. Main power supply connections to the starter 3. Ground strap integrity 4. Fuse box connections related to the fuel pump A disconnected or partially connected plug on the ECU could also cause these symptoms. When working in that area, its easy to accidentally bump these connections. This turned out to be a straightforward fix in my case, though diagnosis took some time to pinpoint the exact connection issue. Would suggest checking all these points before returning to the shop, as loose connections after service work are relatively common. The fact it worked perfectly before suggests its likely related to the recent work rather than a major component failure.

Thanks for the detailed reply about the loose battery connection issue. That makes a lot of sense, especially the point about the voltage drop causing those fault codes while still allowing cranking. I checked my connections following your suggestions and found a damaged wire in the main wiring harness near where they were working. The car won't start reliably until I wiggle that specific area. Did you need any special tools for your repair? Also curious how much the fix ended up costing you and if youve had any related electrical issues since then?

Our issue ended up being a Terminal 15 ignition positive interruption caused by a damaged connection in the wiring. After finding the faulty wire near the ignition switch assembly, getting it properly fixed at the shop cost 95€. They had to repair the cable connection where it meets the relay switch. No special tools were needed for the initial diagnosis, just careful visual inspection of the wiring harness and connector points. The mechanic used their specialized electrical testing equipment to confirm the exact break point in the circuit. Since having it properly repaired, the starter solenoid engages perfectly every time and the electrical system has been completely stable. The original fault codes cleared up immediately after the fix and havent returned. This kind of wiring issue is pretty common after maintenance work where multiple components get disconnected and reconnected. Just make sure when you take it in that they thoroughly check all the connections in that area of the wiring harness, particularly around the fuse box and ignition circuit components. A proper repair should give you the same reliable results.

I took the car back to the shop today and showed them exactly where I found that damaged section in the wiring harness. Turns out they accidentally pinched the wire while reinstalling some components during the previous service. The circuit break was causing intermittent power supply issues to the starter system. The repair only took about an hour, they had to splice in a small section of new wire and properly insulate the connection. Total cost was 75€ for parts and labor. The mechanic also did a full check of the surrounding wiring and fuse box connections to ensure everything else was properly secured. Car starts perfectly now and all the fault codes have cleared. Pretty relieved it was just a simple wiring repair rather than a major electrical problem. Lesson learned though, always check those basic connections first when issues pop up right after service work.