VW T5: Failing Brake Booster Sensor Warning Signs

I dealt with a similar brake system issue on my VW T4 2.0 from 2003. Having some experience with brake repairs, I recognized these symptoms immediately. The reduced braking effect and unusual pedal feel often point to air in the hydraulic brakes. In my case, the workshop discovered the brake system was bled incorrectly during previous maintenance. They also checked the ABS system and pressure sensor connections as part of their diagnostic process. The fix involved a complete professional brake system bleeding procedure using specialized equipment to ensure all air was removed from the lines. Total cost was 90€ for the service. After the repair, brake performance returned to normal and the warning light disappeared. To better assist with your specific case, could you provide: When was your last brake service performed? Does the pedal feel spongy or does it sink to the floor? Are there any unusual noises when braking? Which exact warning light is showing? This information would help determine if your issue matches what I experienced or if further investigation of the replacement parts might be needed. Always recommend having a professional workshop diagnose brake issues, as they are critical safety components.

Last service was in January this year at 98000km. The issue happened suddenly while driving on the highway, which made it particularly concerning. I had to pump the brake pedal several times to get adequate braking power. The warning light shows the standard brake system warning symbol in red. The pedal indeed feels spongy and occasionally sinks further than usual. No unusual sounds during braking. The ABS system seems to be involved since I also noticed the ABS light flickering occasionally. Had my regular mechanic check the pressure sensor readings, but their diagnostic equipment showed inconsistent values. Vehicle safety is my top priority, so I am hesitant to drive until this is properly resolved. The brake booster was actually replaced about 2 years ago, which makes me wonder if the installation could be related to the current problems.

Thanks for those additional details. The symptoms you describe are very similar to what I experienced, but yours sound potentially more serious given the sudden onset at highway speeds. In my T4, inconsistent pressure sensor readings also occurred before my complete repair. The diagnostic tools showed fluctuating values that made no sense, pointing to either a faulty sensor or damaged wiring harness. The fact that your brake booster was replaced 2 years ago is significant. In my repair experience, improper installation of the brake booster can lead to gradual deterioration of brake performance. The pressure sensor connection is particularly sensitive during installation and can become loose over time. My mechanic discovered the pressure sensor wiring had chafed against the brake booster housing, causing intermittent electrical issues. The repair involved: 1. Complete system diagnosis with specialized brake diagnostic tools 2. Replacement of the damaged pressure sensor and wiring harness 3. Verification of proper brake booster installation 4. Full brake fluid flush and system bleeding Total repair costs were around 450€ including all replacement parts. The braking system has worked flawlessly since. Given the safety-critical nature and the symptoms you describe, suggest having the vehicle towed to a workshop specializing in hydraulic brakes and ABS systems for proper diagnosis.

Based on all this information and your advice, I will have the car towed to a specialized workshop tomorrow. The parallels between our cases, especially regarding the pressure sensor readings and brake booster installation, are quite revealing. The brake pedal behavior and ABS system warnings match exactly what you experienced. Your repair details help confirm my suspicion about the pressure sensor being the root cause, possibly complicated by the previous brake booster replacement. The 450€ repair cost seems reasonable considering the comprehensive fix you received. Will ask the workshop to specifically check the pressure sensor wiring near the brake booster housing for potential chafing, along with running their diagnostic tools for a complete system analysis. Really appreciate the detailed breakdown of your repair experience. Having this information helps me enter the repair process better informed. Will update the forum once the workshop completes their diagnosis and repair.