VW Sharan Control System Chaos: Multiple Module Failures

Having worked on cars as a hobby mechanic, I encountered a very similar issue with my 2013 VW Touran diesel. The warning lights and control module problems you describe match my experience exactly. After several frustrating weeks of intermittent system failures and unusual malfunction indicator activations, I took it to my regular workshop. The diagnostic scan revealed multiple error codes across different control units, suggesting a broader communication issue rather than individual component failures. The root cause in my case was a damaged cable connection to the main control module, specifically where it connects to the vehicle BUS system. The repair involved replacing the wiring harness section and ensuring proper shielding of the connections. Total cost was 155€ and completely resolved the engine diagnostics errors and unusual system shutdowns. Before suggesting this might be your exact issue, could you share: Are the issues more frequent when the engine is hot or cold? Which specific warning lights appear most often? Does the problem occur more during acceleration or idle? Have you noticed any correlation with wet weather? These details would help determine if your underlying issue matches what I experienced with the control module connection problem.

Thank you for sharing such a detailed explanation. My service history shows the last inspection was done at 95000km, and these issues started appearing about two weeks ago. The warning signals mainly occur when the engine is warm, usually after 15-20 minutes of driving. The malfunction indicator appears most frequently, followed by the ABS warning light. The system malfunctions happen regardless of acceleration or idle state, but interestingly, they seem worse during damp conditions. The scan tool is showing multiple communication errors across different modules, which matches your experience with the wiring harness issue. I was hesitant to start replacing individual components since the problems seemed interconnected. Your solution of checking the main control module connections makes a lot of sense given the similar symptoms. Will have the workshop check the wiring harness and BUS system connections first before exploring other options.

Thanks for providing those additional details about the timing of the warning signals and system behavior. The correlation with damp conditions and warm engine state strongly reinforces my initial suspicion about the wiring harness issue. When I dealt with this on my Touran, the scan tool also showed those scattered communication errors across multiple control modules. The timing of your malfunctions, appearing after 15-20 minutes of warm-up, exactly matches what I experienced before discovering the damaged connection. The way your ABS warning light behaves alongside the malfunction indicator definitely points to a communication problem rather than actual system failures. In my case, the engine diagnostics initially suggested multiple separate issues, but they were all symptoms of the compromised wiring connection. The correlation with moisture is particularly telling. When my control module connection was damaged, water infiltration would cause temporary system failures and trigger various error codes. Having the workshop focus on the wiring harness and BUS connections first is absolutely the right approach given these symptoms. One quick check you can do before the workshop visit: look for any visible corrosion or damage around the main wiring connections near the engine control module. This might give the technicians a head start on locating the exact problem area.

The symptoms you describe with the wiring harness match my situation perfectly. I appreciate the confirmation about focusing on the connections first, especially since the issues get worse in damp conditions. I checked around the engine control module area as suggested and noticed some discoloration on one of the main connectors. This seems to line up with the theory about moisture affecting the system failures and triggering those unusual error codes. I have scheduled a service required for next week, specifically asking them to inspect the wiring harness and BUS system connections. Given how closely my symptoms match your experience, especially the timing after warm-up and the correlation with damp weather, I feel much more confident about the potential fix. Will update once the workshop completes their inspection and hopefully confirms the wiring harness as the root cause of these control module issues. The repair cost you mentioned gives me a good reference point for what to expect. Thank you for helping narrow down the likely cause rather than having them replace various components through trial and error.