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vivienschwarz10

RS3 Multiple Electrical Failures Baffle Mechanics

Fault stored

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Sporadic errors when driving or sporadically illuminated error lights in the speedometer

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Failure of various systems (mostly in the area of audio/navigation functions)

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Electrical systems react very slowly

My 2012 RS3 is acting really weird lately, getting unusual error messages and the infotainment system keeps glitching out. Sometimes control units just stop working completely. The check engine light comes on and off, and my OBD-II scan tool shows multiple stored error codes. Last mechanic visit was a disaster and didnt fix anything. Running a 2.5L gas engine with 163k on the clock. Has anyone experienced similar electrical gremlins? Looking for advice before picking another shop to diagnose this mess.

4 comment(s)


marvinhimmel5

Had similar issues on my 2015 S3 2.0T. The symptoms match what I experienced, unusual system failures, warning lights cycling, and multiple error codes showing up during engine diagnostics. The root cause was a deteriorated cable harness connecting the main control unit to the vehicle BUS system. These connections get corroded over time and create intermittent connectivity problems. When the BUS communication fails, it triggers multiple warning lights and causes various control units to malfunction. This is a serious electrical issue that requires proper diagnosis with professional scan tools. The generic OBD-II readers often cant properly communicate with all control modules to pinpoint the exact failure point. The fix involved replacing the main wiring harness and reestablishing proper connections to the BUS system. After repair, all system communications were restored and error codes cleared permanently. The check engine light and other electrical issues never returned. Would strongly recommend finding a shop that specializes in electrical diagnostics for German vehicles, as this requires specific expertise and testing equipment to properly diagnose and repair.

vivienschwarz10 (Author)

Thanks for sharing your experience. For my RS3, I had nearly identical issues with the unusual error messages and failing control units. The service required light kept coming on and off out of nowhere too. The wiring harness replacement fixed everything for me just like in your case. The warning lights disappeared and all systems are working perfectly now. The engine diagnostics show everything is back to normal. Quick question, do you remember roughly how much you paid for the repair? And has everything stayed working properly since the fix? Wondering if any other electrical gremlins popped up later.

marvinhimmel5

After getting it properly diagnosed and fixed at a reputable shop, I can confirm everything has stayed working perfectly for over 8 months now. Not a single control module error or system failure has appeared since the repair. The total cost for my repair was 155 Euro, which covered fixing the faulty cable connection between the control unit and the BUS system. This was significantly less expensive than I initially feared, given how complex these electrical issues can seem. My OBD-II scan tool now shows zero stored codes, and all vehicle systems are communicating properly. The unusual warning lights and electrical glitches have completely disappeared. It really highlights how important proper engine diagnostics are, getting to the root cause rather than just clearing codes makes all the difference. Glad to hear your RS3 is also running well after the fix. These electrical issues can be frustrating, but once properly repaired, they typically dont return.

vivienschwarz10 (Author)

After trying multiple shops, I finally found a specialist who properly diagnosed the malfunction indicator issues. The scan tool revealed exactly what you mentioned, corrupted communication between the control modules due to damaged wiring. Took it in last week and the repair cost was 180 Euro for the wiring harness replacement. The service required light hasnt come back since. All systems are now working perfectly, no more unusual errors or glitchy displays. The mechanic showed me the corroded wiring that was causing all these problems. Amazing how such a small issue can affect so many vehicle systems. Really glad I got a proper diagnosis instead of continuing to clear codes without fixing the root cause. Thanks again for pointing me in the right direction. Would have spent way more time and money troubleshooting without your advice about the wiring harness being the likely culprit.

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