SQ5 ABS Warning Linked to Speed Sensor Malfunction

As someone with moderate repair experience, I encountered a similar issue on my 2012 S4. The ABS warning light and traction control problems matched your symptoms exactly. The diagnostic scan revealed a faulty ABS control unit, which was affecting the speed sensor input signals. Despite the speedometer working normally, the ECM wasnt receiving reliable data from the ABS module for proper traction control operation. After multiple attempts to resolve it through sensor cleaning and wiring checks, the workshop confirmed the control unit itself was defective. The transmission control was also occasionally showing erratic behavior due to this issue. Total repair cost was 1000 Euro, including programming and testing. The repair process took about 4 hours, but the results were worth it, all systems have worked flawlessly since then. Could you share: Current mileage, Whether you notice any unusual sounds during braking, If the issue started suddenly or developed gradually, Any other warning lights present This information would help determine if your case is similar and whether you might be looking at the same repair path.

Thanks for sharing your experience. My vehicle has 111211 KM on the clock from the latest service. My ABS issue started gradually over the past few weeks. No unusual sounds during braking, but the ABS sensor seems to be acting up more frequently in wet conditions. The only warning light active is the ABS indicator, no other dashboard warnings present. Based on your feedback, I will have the workshop check the ABS control unit specifically, since the symptoms align closely with your case.

Thanks for the mileage and symptom details. After fixing my S4s ABS control unit, I learned these systems can be sensitive to environmental conditions. The behavior you describe in wet conditions matches what I experienced before the repair. Your mileage is actually close to when my ABS issues started developing. The diagnostic codes from the ECM should help confirm if the control unit is the culprit, but the matching symptoms, especially the gradual onset and weather sensitivity, strongly suggest a similar root cause. Since your speedometer still works correctly while the ABS shows faults, this reinforces my suspicion of the control unit rather than individual speed sensors. The transmission and traction systems rely on accurate input from the ABS module, so intermittent faults like this typically point to the control unit itself. When you take it to the workshop, request that they: 1. Check all sensor connections first 2. Perform a full diagnostic scan of the ABS module 3. Verify the control unit programming version This approach helped avoid unnecessary parts replacement in my case. The repair ended up being straightforward once properly diagnosed.

Based on your repair details and thorough diagnostic suggestions, I feel more confident about addressing my ABS issues. My speedometer readings stay accurate, which aligns with your experience of the ABS control unit being the likely culprit rather than individual sensors. The weather-related symptoms you mentioned match my situation perfectly. Since my dashboard only shows the ABS warning without other indicators, and given the similar mileage when these problems started, I will proceed with your suggested diagnostic steps. I have scheduled a workshop visit for next week and will specifically request they follow the three-step check process you outlined. The 1000 Euro repair cost you mentioned helps set realistic expectations for my budget. Will make sure they verify all sensor connections before replacing any components. Thanks again for the detailed insight. The gradual onset of my ABS malfunction combined with these specific symptoms makes me feel more certain about the diagnosis path forward.