VW Scirocco CAN Bus Issues Trigger Cooling Failure

Having experienced a similar issue with my 2006 Golf GTI, I can share some relevant insights about control module problems. The symptoms you describe match what I encountered, coolant issues combined with control unit communication faults. My diagnostic scan also showed multiple CAN bus errors, suggesting a connectivity issue between the engine control module and cooling system components. After some troubleshooting, my workshop found a damaged wiring harness causing a data link failure between the cooling fan control module and the main ECU. The connection had deteriorated over time, leading to intermittent communication faults. The repair involved: Complete diagnostic scan, Testing all control module connections, Replacing damaged wiring and connectors, Reprogramming the control unit Total cost was 95€ and resolved both the overheating and warning light issues. To better assist with your specific case, could you share: Which diagnostic trouble codes you received? Is the overheating constant or intermittent? Have you noticed any other electrical issues? When did these symptoms first appear? This information would help determine if your Scirocco is experiencing the same underlying control module communication problem I encountered.

Thanks for the detailed explanation. My issues started about 2 weeks ago, right after my last service at 11526km. The diagnostic trouble codes I got are P0217 and P0128, pointing to engine overheating and coolant thermostat problems. The overheating happens mostly during city driving, less on highways. The car diagnostic system shows sporadic CAN bus communication errors between the engine control module and cooling system. Other electrical issues include unusual instrument cluster flickering and occasional AC control panel unresponsiveness. The software glitch seems to affect multiple systems, making me think the root cause might be similar to your wiring harness problem. Wondering if I should start with checking the wiring connections or go straight to a full diagnostic scan at a specialized workshop?

Thanks for providing those details. Like you, my issues also emerged shortly after routine maintenance, and those trouble codes match exactly what I experienced. The combination of P0217 and P0128 with the CAN bus errors strongly suggests a wiring issue affecting multiple control modules. The instrument cluster flickering you mentioned mirrors my experience, it was one of the first signs before the major cooling system problems developed. In my case, starting with a basic wiring check actually wasted time. The intermittent nature of connectivity issues made them hard to spot during simple visual inspections. The specialized diagnostic equipment at the workshop was necessary to pinpoint the exact location of the wiring harness fault. My recommendation based on experiencing this exact scenario: Skip the basic checks, Go directly for a full car diagnostics scan, Request specific testing of the control module connections, Have them check the wiring harness near the coolant temperature sensor The fact that your issues are less severe on highways matches my experience, the car diagnostics revealed this happens because highway speeds create different cooling demands and control unit communication patterns. The repair costs should be similar to what I paid (95€), assuming the root cause is indeed a comparable wiring harness issue affecting the control unit communication.

I appreciate the thorough advice about going straight to a workshop. The similarity between our cases is quite striking, especially the timing after maintenance and identical diagnostic trouble codes. I scheduled a full diagnostic scan for next week at a shop specializing in control module issues. They confirmed they will test all the wiring connections and control unit communication patterns you mentioned. Just today the instrument cluster started acting up even more frequently, and the engine temperature warning appeared twice during a short drive. The software glitch seems to be getting worse, reinforcing that this is likely a wiring issue affecting multiple systems. Will update once the workshop completes their diagnostic scan and hopefully resolves these control module communication errors. The 95€ cost estimate helps set my expectations for the repair. Really hoping its just a damaged wiring harness like in your case and not a more complex control unit failure.