Audi Q7 TDI Brake Booster Sensor Failure Alert

I faced a similar issue with my 2012 Audi Q5 TDI. Having some experience with brake system repairs, the symptoms you describe closely match what I encountered. Initially, my hydraulic brakes started showing reduced effectiveness, and the brake pedal felt unusually hard. The workshop diagnosed it as incorrectly bled brake lines, which was causing air pockets in the system. The repair involved a complete brake fluid flush and proper bleeding of the brake system, costing 90 Euro. However, your case might be different since youre mentioning warning messages and fault codes. Before jumping to conclusions about the brake booster, it would be helpful to know: Which specific warning messages appear on your dashboard? When does the reduced braking power occur (cold start, after driving)? Have you noticed any unusual sounds when pressing the brake pedal? Did you recently have any brake work done? These details would help determine if its a simple bleeding issue like mine or if replacement parts for the brake booster system are needed. Vehicle safety isnt something to take chances with, so getting an accurate diagnosis is crucial.

Thanks for the detailed input. Last service was at 187000km, about 4 months ago. The warning messages appear immediately after starting the car, showing ABS system failure and brake system malfunction. The brake pedal feels hard consistently, not just during cold starts. The reduced brake performance is noticeable all the time, making the car unsafe to drive. My local workshop checked the fault codes which point to the brake booster and pressure sensor malfunction. They quoted 850 Euro for parts and labor. Before proceeding, I wanted to confirm if this matches others experiences with similar brake system issues in terms of symptoms and repair costs. No recent brake work was done besides regular fluid changes during scheduled maintenance. The hydraulic brakes worked perfectly fine until last week when the issues started suddenly during normal driving.

Thanks for providing those additional details about your Q7s brake system problems. Your symptoms are nearly identical to what I experienced with my Q5, and the sudden onset matches my case exactly. After my initial misdiagnosis with brake bleeding, the real issue was indeed the brake booster pressure sensor. The ABS system warnings and consistent hard pedal feel are telltale signs. The quote of 850 Euro is actually reasonable, I ended up paying 890 Euro for the complete repair on my vehicle. The brake booster repair resolved all issues: Warning messages disappeared, Normal brake pedal feel returned, ABS system functionality was fully restored, Overall brake performance returned to normal One important note, make sure they run a complete diagnostic on the entire brake system after the repair. In my case, the faulty sensor had caused some minor calibration issues in other components that needed adjustment. The repair took about 4-5 hours in total, and the vehicle safety systems worked flawlessly afterward. Given your mileage and the sudden failure, this is a fairly common wear point for these models.

Thank you for all these helpful replies. I will proceed with the brake booster and pressure sensor replacement as suggested. The matching symptoms and similar repair costs you mentioned have given me confidence in my workshops diagnosis. Its reassuring to know this is a common issue with a proven fix. Since my vehicle has high mileage and the brake performance is severely compromised, I will schedule the repair immediately. Your insight about checking the entire brake system afterward is particularly valuable. I will make sure to request a complete diagnostic check of all brake components and ABS system calibration after the repair. Will update the forum once the work is completed in case others face similar issues in the future.