RS4 Turn Signal Issues: Diagnostic Help Needed

As someone with some repair experience, I faced an almost identical issue with a 2018 RS5 last summer. The signal lamp problems and error messages turned out to be more than just a basic bulb replacement case. The root cause was actually a damaged wire connection near the flasher relay. The workshop found that moisture had corroded one of the plug connections, causing intermittent signal failures and triggering the error messages on the dash. The fix involved: 1. Complete diagnostic scan to pinpoint the exact connection issue 2. Cleaning the corroded plug contacts 3. Replacing the damaged wiring section 4. Testing the entire signal lamp system Total repair cost was 95 Euro, covering both diagnostics and the wiring fix. Much better than replacing parts unnecessarily. To provide more specific advice for your case, could you share: Are the turn signals completely dead or working intermittently? Does the error occur on one side only? Have you noticed any moisture or water ingress around the lighting assemblies? When did the problem first appear? This information would help determine if your issue matches what I experienced with the faulty connections.

Thanks for checking. My mileage is at 122043 KM, with the last maintenance done at the official service center 3 months ago. The turn signals are completely dead on the right side, and the error occurs only there. The electrical fault seems consistent rather than intermittent. No visible moisture around the lamp housing or broken lens that I can spot. The issue started suddenly last week during a rainy day. Before going for a full diagnostic scan, I would appreciate any other troubleshooting steps to try first.

Based on your description, this sounds very similar to what I experienced with my RS5. Since your issue is isolated to the right side and started during rain, it strongly suggests a connection problem rather than a flasher relay fault. Before going for diagnostics, try these steps that helped identify my issue: 1. Check the indicator light bulb on the right side first, while probably not the main issue, its worth ruling out a simple bulb failure 2. Inspect the wiring harness connection points near the right signal lamp assembly 3. Listen for the clicking sound from the flasher relay when activating the right turn signal 4. Test both front and rear signal lamps on the right side, as sometimes the issue affects only one of them In my case, the complete failure on one side pointed directly to a wiring issue rather than an electronic control problem. The fact yours started during rain matches my experience with water infiltration, even though visible moisture isnt apparent now. A full diagnostic scan ended up being necessary for my repair, but trying these basic checks first will help pinpoint whether you are dealing with the same wiring connection issue I had. Let us know what you find after checking these points, especially the condition of the connector pins at the lamp assembly.

Thanks for all the detailed suggestions. I followed your troubleshooting steps and found something interesting. When checking the right side signal lamp connections, I noticed one of the connector pins appears slightly corroded. The flasher relay does make a clicking sound, but the automotive lighting remains dead on that side. No issues with the bulb itself after testing it in the left turn indicator housing. I think you were right about the wiring connection being the likely culprit. Given that both front and rear signals are affected on the right side, and considering how the problem started during rain, Im going to focus on that corroded connector first before paying for a full diagnostic scan. Would you recommend attempting to clean the connector pins myself, or should I leave that to a professional given the complexity of the electrical system? The repair cost you mentioned seems reasonable compared to out of nowhere replacing parts.