VW Touran's Electrical Nightmare: Multiple System Failures

I had a very similar issue with my 2004 VW Golf which is built on the same platform. With some experience working on VWs, I can share what happened in my case. The unusual warning lights, multiple error codes, and intermittent failures across different systems pointed to a communication problem between control modules. After connecting an OBD-II scanner, my workshop found that the main control module had a damaged wiring connection to the CAN-BUS system. The service required included: Complete diagnostic scan, Testing all control module connections, Replacing damaged wiring harness connectors, Reprogramming the control module Total repair cost was 155€ and completely resolved the unusual warning signals and system failures. Before suggesting more specific solutions, could you share: Are the issues more frequent when the engine is hot or cold? Which specific warning lights appear? Have you noticed any correlation with wet weather? Can you list the error codes from your scan? These details would help confirm if your issue matches what I experienced with the control module wiring.

Thanks for the detailed information. Just wanted to add that at my latest service 2 weeks ago, the mechanic did a full engine diagnostics scan and found no major issues, which makes these new electrical problems even more puzzling. The control module issues seem worse when starting up cold, especially during the first 5 minutes of driving. The malfunction indicator light typically appears first, followed by the audio system shutting down. The OBD-II scan shows error codes P0603 and P0606 among others, which apparently point to internal control module memory issues. This makes me think the root cause might be different from your wiring harness problem, possibly a failing module itself. Will try to gather more detailed data about the exact sequence of failures before taking it back to the shop.

Thanks for providing those additional details about the timing of issues and specific error codes. This does change my initial assessment based on my Golf experience. The P0603 and P0606 error codes, combined with cold-start issues and the malfunction indicator pattern, strongly suggest an internal ECM (Engine Control Module) problem rather than the wiring harness issue I initially encountered. My repair journey took an unexpected turn when similar symptoms appeared again six months after fixing the wiring. The scan tool revealed the same error codes you mentioned, and it turned out the control module itself was failing internally. The repair required: ECM replacement, System reprogramming, Key code adaptation The total cost came to 890€, significantly more than my first wiring repair, but it permanently resolved all warning signals and system malfunctions. Before proceeding with module replacement, suggest having the workshop: Verify ECM ground connections, Check battery voltage under load, Monitor CAN-BUS communication during cold starts This could rule out any power supply issues causing the control module to malfunction.

I appreciate this thorough feedback about ECM issues. After reading about your experience, I feel more confident about the diagnosis of my Touran problems. The cold start symptoms and service required warnings match exactly what you described. The OBD-II warning signals have become more frequent this week, and the malfunction indicator now stays on longer each time. Based on the error codes and your repair experience, I suspect I am looking at a similar ECM replacement. Your repair cost information is particularly helpful. I will budget around 900€ for the fix and make sure the workshop checks those power supply connections you mentioned before replacing any components. I have documented all system failures and warning light patterns over the past few days to share with the mechanic. Will schedule the engine diagnostics for next week and request they specifically check the ECM ground connections during cold starts. Good to know what to expect with the key programming requirements too. This helps me prepare for the full scope of the repair process.