Multiple Audi S4 Error Codes Point to Control Module

As someone with some hands-on experience working on Audis, I had a very similar issue with my 2002 Audi A4. The symptoms were nearly identical, multiple system errors, check engine light, and various warning messages across different displays. After getting a proper diagnostic scan with a professional scan tool, it turned out the malfunction indicator was triggered by incorrect coding in the control module. The fault codes were showing up because the module settings didnt match the actual vehicle configuration. Had this fixed at a specialized workshop that knew their way around Audi control modules. The total repair cost was 360 Euro, which covered the diagnostic work and recoding of the module. After the fix, all error messages disappeared and havent returned. Before suggesting specific solutions, could you share: Have you had any recent repairs or battery replacements? Which specific fault codes is your control module showing? Are all errors appearing simultaneously or did they start one by one? What does your scan tool report for the transmission control module? This information would help determine if your S4 is experiencing the same coding issue I encountered with my A4.

Thanks for the input. At 196253 KM, these issues can definitely be age-related. I hooked up my OBD-II scanner after seeing your reply and got codes P0441 and P0455, pointing toward an EVAP system problem. The check engine light started flashing intermittently before becoming solid. The last service was done 3 months ago, including a new battery install. Errors started appearing gradually over 2 weeks, first the infotainment, then instrument cluster warnings. No transmission codes showing in the diagnostic scanner readings. One thing I noticed, the gas cap seems a bit loose, which could explain the EVAP codes. Going to try replacing that first as a simple fix before diving deeper into the control module recoding.

I can relate to your situation with the EVAP codes. After I dealt with the control module issues on my A4, I also encountered P0455 about six months later. The gas cap was indeed the culprit in my case too. Before spending money on module recoding, definitely try replacing the gas cap first, it solved the evap system fault codes on mine. The check engine light cleared itself after about 50-60km of driving once I installed the new cap. Just keep in mind that while the gas cap might fix the EVAP codes, the infotainment and cluster errors could be separate issues. On my A4, these multiple system warnings were actually caused by voltage fluctuations from the battery not being properly coded after replacement. The new battery installation needs to be registered in the control module, something many regular shops skip. Suggest getting the battery coding checked since you mentioned a recent replacement. When improper battery coding triggers multiple system faults, resetting codes alone wont solve it. The malfunction indicator will just keep coming back until the module knows the correct battery specs. Let us know if the new gas cap makes any difference to the fault codes. That way we can better determine if you need to look into the battery coding issue I experienced.

Thanks everyone for the suggestions. I just installed a new gas cap (22 Euro) and cleared the engine diagnostics with my OBD-II scanner. After about 200km of driving, the EVAP system codes havent returned and the check engine light is staying off. However, the infotainment and instrument cluster errors are still present. Taking it to a specialized workshop next week to check the battery coding issue mentioned here. The service advisor confirmed they can verify if the control module needs updating after the recent battery replacement. Will post an update once I know if the battery registration fixes the remaining error messages. Really glad I checked here before spending money on unnecessary parts, between the diagnostic scanner readings and your similar experiences, I have a much clearer direction for the repairs.