Audi S4 Door Lock System Failure and Solutions

Having some experience with car electrical issues, I faced a similar problem on my 2010 S5. The automatic locks stopped working and the central locking system became unresponsive, though like yours, the car alarm remained functional. After inspection, my workshop found the wiring harness had a damaged connection at the door contact sensor. The cable insulation was worn through, causing intermittent electrical issues. The total repair cost was 95 Euro, which covered replacing the affected wiring section and testing all door functions. This is often caused by repeated door movement wearing down the wire coating where it flexes. The good news is its typically a straightforward fix once properly diagnosed. Could you share: Whether you notice any warning lights on the dashboard, If you hear any clicking sounds when using the key fob, Whether this affects all doors or just specific ones, If the issue is constant or intermittent These details would help determine if your problem matches what I experienced or if its something else in the electrical system. The fix worked perfectly in my case and all automatic locks have functioned normally since the repair.

Last service was at 9300 KM. The door latch on the driver side makes an unusual clicking noise when using the remote. After reading your detailed reply, I suspect its similar to your case with the wiring. There are no warning lights showing on the dash, but the electrical issue affects all doors consistently. The contact signal seems completely dead, no response from any automatic locks when using the key fob or interior switches. The car sensor system still shows all doors are closed though. Will have it checked at the workshop this week. Thanks for sharing your experience with the wiring harness problem.

Thanks for the follow-up details. Those symptoms match my experience exactly, especially the clicking sound from the door latch, which was also present in my case before the repair. The fact that your car sensor still recognizes the doors as closed while the locks are unresponsive strongly suggests a wiring harness issue rather than a faulty door sensor itself. Quick tip from my repair: have the workshop specifically check the wiring bundle where it passes through the rubber boot between the door and body. This is where my door switch wiring failed, as the constant movement had worn through the protective covering. The clicking noise you describe from the driver side door latch is a telltale sign, it means the lock motor is receiving some power but not the proper signal from the door contact system. In my repair, they needed to replace about 20cm of the wiring harness section that connects to the door sensor. Let us know what the workshop finds. If it is indeed similar to my case, you should expect a relatively quick fix once they locate the damaged section of wiring.

Thanks for the input. Just got back from the workshop and wanted to close this thread with the outcome. You were right, it was exactly the wiring harness issue you described. They found worn cables near the door contact sensor on the driver side, right where it passes through that rubber boot section. The repair took about 2 hours and cost 120 Euro including parts. They replaced the damaged section of the wiring harness and tested all vehicle doors thoroughly. The automatic locks are now working perfectly again, no more clicking sounds and all door functions are back to normal. The car alarm and central locking system are both responding correctly. Really appreciate the help in diagnosing this. Having the specific info about where to look saved time at the workshop. Would definitely recommend others with similar door sensor issues check their wiring first before assuming more complex problems.