Audi S3 Knock Sensor Issues: Warning Signs & Solutions

I had nearly identical car problems with my 2004 Audi A3 2.0T. After dealing with similar symptoms, poor fuel efficiency, rough idling, and constant check engine light, I took it to a workshop for diagnosis. The mechanic first ran a diagnostic scan which pointed to knock sensor issues. They checked the wiring and found that the cable connection to the knock sensor had deteriorated over time, causing intermittent signal problems. This can often be mistaken for a faulty sensor itself. The repair was relatively straightforward. Total cost was 95 Euro for replacing the wiring harness and testing to ensure proper sensor communication. The whole job took about 2 hours. After the fix, engine performance returned to normal and fuel consumption improved significantly. To properly assist with your S3 auto repair situation, could you share: Have you had any diagnostic codes read? Did these engine knock symptoms appear gradually or suddenly? Are there any unusual sounds when accelerating? What is your current mileage? These details would help determine if your issue matches what I experienced or if further investigation might be needed.

Thanks for sharing your experience with the knock sensor issue. My S3 just had its service at 68389 KM and the malfunction indicator light came on shortly after. The symptoms appeared quite suddenly after a cold start. The diagnostic scan showed code P0325, pointing to the knock sensor circuit. The engine does make a slight pinging sound during acceleration, especially under heavy load. My mechanic suggested testing the wiring first since the warning light started right after the service. Makes me wonder if something got disturbed during maintenance. Good to hear your repair was straightforward. The quoted cost for my diagnostic work is 120 Euro which seems reasonable based on your experience. Planning to have it checked next week to prevent any long-term engine damage.

Thanks for the additional details. Having experienced similar issues with my A3, that P0325 code combined with the pinging sound during acceleration definitely aligns with knock sensor circuit problems. The timing of your symptoms appearing after service is particularly telling, we often see these ignition timing issues emerge when components are disturbed during routine maintenance. In my case, the fuel efficiency dropped by about 15% before fixing the wiring harness. The check engine light issue was definitely stress-inducing, but catching it early prevented any serious engine damage. The 120 Euro diagnostic fee is in line with what I paid. Since your symptoms match my experience almost exactly, I strongly suspect you will find damage to the wiring harness rather than a completely failed sensor. Make sure they thoroughly inspect the connector pins for corrosion while they are at it. One tip from my repair experience: ask them to check the sensor mounting torque. My mechanic found that improper torque can cause similar symptoms and it is worth verifying since the area was recently accessed during service.

The diagnostic code P0325 and your experience with the wiring harness issue matches exactly what I was concerned about. Realizing these car problems started right after service definitely makes me think something got knocked loose during maintenance. The pinging during acceleration is a classic symptom I keep reading about with knock sensor problems. Your repair cost breakdown gives me a good reference point. The 120 Euro diagnostic fee my shop quoted seems fair, especially since they will do a full circuit check. Your tip about checking the mounting torque is particularly helpful, I will definitely ask them to verify this since the area was accessed during the recent service. The poor performance and increased fuel consumption are becoming more noticeable, so I am glad I scheduled the repair for next week. The malfunction indicator light has been a constant reminder something needs attention. Really hoping it is just a wiring issue like in your case rather than a complete sensor replacement. I appreciate the detailed feedback about your experience. Will update once I get the final diagnosis and repair completed. Hoping for a simple fix like yours to restore normal engine operation and fuel efficiency.