Audi A5 Brake Booster Sensor Failure Warning Signs

Had a similar issue with my A4 (2018, 2.0T). The brake performance gradually declined over a few weeks, showing identical symptoms, spongy pedal feel and requiring more pressure to stop effectively. The root cause was actually two-fold: incorrectly bled hydraulic brakes combined with a faulty brake booster sensor. The initial diagnosis missed the sensor issue because they focused solely on the brake fluid system. The warning lights persisted even after the first bleeding attempt. When properly diagnosed, they found air pockets remained in the system after an incomplete bleeding procedure, and the brake booster sensor was sending incorrect signals to the control module. The complete fix required: Full system diagnosis with specialized brake sensor testing equipment, Complete brake fluid flush and proper bleeding sequence, Replacement of the brake booster sensor, Recalibration of the brake control module This was a serious safety concern that required immediate attention. The compromised brake performance could have led to significantly longer stopping distances. The repair shop needed specific diagnostic tools to properly identify the dual nature of the problem. Key point: Ensure the shop does both electronic diagnosis and mechanical inspection of the entire brake system, not just one aspect.

Thanks for sharing your experience. Exact same situation happened with my Audi A5. The brake pedal started feeling weird and the warning lights had me worried about vehicle safety. Following your advice, I found a shop that did a thorough brake system inspection and replaced both the sensor and did a complete fluid flush. Just curious, do you remember the total cost for the replacement parts and labor? Also, has your brake booster been working fine since the fix, or did you notice any other issues?

Since getting my A4 fixed, the brake booster pressure sensor has worked flawlessly. The complete repair was surprisingly affordable at just 90 Euro, which covered the brake system bleeding that was initially done incorrectly. The ABS system now functions perfectly, and the brake pedal feels firm and responsive again. The warning lights disappeared immediately after the repair, confirming the diagnostic tools identified the correct issue. The hydraulic brakes have maintained consistent performance with no soft pedal feeling or other concerns. My advice would be to always ensure any brake system repairs are completed by technicians using proper diagnostic tools and following the correct bleeding sequence. Its been over a year since the fix, and I havent experienced any related issues with the braking performance.

Thanks for the feedback. Went to a specialized shop yesterday and the experience was totally different from my first attempt. The mechanic used advanced diagnostic tools to properly identify the failing brake booster sensor. The total repair came to 650 Euro, more than I expected but worth every cent for proper brake performance and peace of mind. They did a complete system flush, replaced the pressure sensor, and recalibrated everything. The brake pedal feels solid now, all warning lights are gone, and the hydraulic brakes work perfectly again. The technician showed me the old sensor which had obvious corrosion. He explained how their specialized testing equipment detected the inconsistent signals it was sending. Really glad I got a second opinion and proper fix rather than just living with the issue. Nothing beats the confidence of knowing your brakes are working exactly as they should.