VW Touran Brake Booster Sensor Failure Alert

I had a very similar issue with my 2019 VW Tiguan TSI. As someone with some experience working on cars, I initially thought it was just air in the brake lines, but it turned out the brake system was not properly bled during a previous service. The symptoms matched yours exactly, reduced brake performance and warning lights. The brake pedal felt spongy and had more travel than usual. My vehicle safety was definitely compromised, so I took it to a workshop right away. The repair took about 2 hours. The technician performed a complete brake system bleed using professional equipment to ensure all air was removed. Total cost was 90€ for the service. After the repair, the brake booster and pressure sensor worked perfectly again, and the pedal feel returned to normal. Before suggesting specific fixes, could you share: When was your last brake service? Does the pedal feel spongy or just harder to press? Are you getting any specific error codes? Has any recent work been done on the brake system? This information would help determine if your issue is similar to what I experienced with the brake system bleeding, or if the pressure sensor truly needs replacement parts.

Last service was 6 weeks ago where they changed brake fluid and performed a full inspection. The brake pedal feels harder to press, not spongy. The ABS system warning light keeps flashing and diagnostic tools show error code P0504. Since my visit to the workshop, the brake system warning appears intermittently, especially during cold starts. The brake booster seems to work partially, but braking requires significantly more force than before. The brake pedal behavior is inconsistent, sometimes it returns to normal operation for short periods. A mechanic mentioned the brake booster vacuum line might also be worth checking before replacing the pressure sensor. The problem started appearing shortly after reaching 15635km. Would it be worth getting a second opinion from another workshop, considering the recent service didnt identify any issues?

Based on your description and my own experience with the same issue, this really sounds like the brake booster pressure sensor. The error code P0504 matches what I had, and the intermittent nature of the problem is a typical symptom. After my brake system was bled without solving the issue, I eventually had the pressure sensor replaced. The repair cost was around 280€ including parts and labor. The ABS system warning light disappeared immediately after the sensor replacement. The inconsistent brake pedal behavior you describe mirrors my experience exactly. The varying brake performance and particularly the cold start issues are classic signs of a failing pressure sensor, not a vacuum line problem. Since your brake fluid was recently changed, we can likely rule out contamination or air in the system. The fact that the brake pedal feels harder rather than spongy also points away from vacuum line issues. Given your mileage and the symptoms, getting a second opinion might just delay fixing the actual problem. The pressure sensor is a known wear item that can fail even on relatively new vehicles, affecting overall brake performance and vehicle safety. Consider asking the workshop to specifically check the sensor readings with a diagnostic tool when the system is both cold and at operating temperature. This helped identify the issue conclusively in my case.

Thanks for the detailed information about your experience with the brake booster sensor replacement. My symptoms do match exactly what you described, especially the intermittent behavior and cold start issues. I called another workshop and they confirmed the brake system diagnostic points toward the pressure sensor. They quoted 295€ for the replacement parts and labor, which seems reasonable compared to your repair cost. The technician also mentioned they can verify the sensor readings at different temperatures to confirm the diagnosis. Makes sense that the brake performance issues and ABS system warnings are linked to the sensor rather than the vacuum line, especially given the error code and symptoms. Since the recent brake fluid service ruled out contamination issues, I will go ahead and schedule the pressure sensor replacement next week. The inconsistent brake pedal behavior is concerning from a safety perspective, so better to address it promptly rather than risk further brake system problems. Will update once the repair is completed to confirm if it resolved the warning lights and restored normal braking performance.