Audi SQ5 Electrical Chaos: Multiple System Failures

Had a similar issue with my 2012 S4, and with some experience working on Audis, I can share what worked for me. The unusual warning light activation and system failures you describe match exactly what I encountered. The malfunction indicator would flash intermittently, and various systems would act erratically. After multiple diagnostic attempts, my workshop found the root cause: a faulty cable connection to the main control unit that connects to the BUS system. The repair involved: 1. Complete diagnostic scan of all control modules 2. Testing the communication between units 3. Replacing and properly securing the cable connections 4. System reset and recalibration Total cost was 155 Euro, and it completely resolved the warning signals and system failures. The workshop explained that these issues often stem from deteriorated connections rather than the control units themselves. Before suggesting specific solutions, could you share: Current mileage, Any recent repairs or modifications, When the issues first appeared, Whether the problems occur more frequently when the engine is hot or cold, If any specific events trigger the service required messages This information would help determine if your case is similar to what I encountered.

Thanks for sharing the details about the control module issues. Following my last service at 70139KM, I had the engine diagnostics run but no major faults were detected. The warning light problems started showing up about two weeks after that check. The check engine light seems to activate mostly during cold starts, which might point to different root causes than your S4 case. The infotainment crashes happen regardless of engine temperature though. I will try to monitor and document when exactly these OBD-II errors occur to help pinpoint the issue. I appreciate the repair steps you outlined, will take it to get the connections checked and tested as suggested.

Thanks for the additional details about the cold start symptoms. While my S4 showed similar warning light patterns, you raise an interesting point about the timing. In my case, the malfunction indicator was more unusual, not specifically tied to cold starts. The BUS system connection fix worked for my infotainment issues, but your cold start pattern suggests checking additional components. Specifically, given your OBD-II error timing, I would recommend having the workshop test: 1. Battery voltage and charging system 2. Ground connections, especially engine grounds 3. Main control unit power supply during cold starts The service required warnings during cold starts often point to voltage-related issues that the BUS system connection repair alone might not resolve. When my S4 had similar symptoms, the workshop found that poor ground connections were amplifying the control unit communication problems. Consider having a voltage drop test performed during a cold start sequence. This helped identify the root cause in my case more accurately than standard OBD-II diagnostics alone.

The cold start information is really helpful in narrowing down these system failures. My mileage is now at 72000KM, and I noticed the problems are most frequent in the morning after the car sits overnight. Based on your voltage suggestion, I had the battery tested yesterday. Its showing normal voltage but the workshop mentioned possible inconsistent power delivery during startup. They want to do a complete electrical system diagnostic including the ground connections you mentioned. The OBD-II scan showed multiple transient errors, but interestingly, they clear themselves after the engine warms up. This matches what you mentioned about voltage-related issues being different from the BUS connection problems. I will schedule the suggested voltage drop test next week. The warning signals during cold starts are becoming more frequent, so getting this resolved soon is important. The service required message now appears almost every morning, though it usually clears after about 10 minutes of driving. Thanks for sharing your experience, having a clear diagnostic path helps tremendously with these control module issues.