VW Fox Brake Issues? Check Booster Pressure Sensor

I had a similar issue with my VW Polo diesel from 2011, and being somewhat experienced with basic car maintenance, I initially thought it was something major. The symptoms were exactly like yours, ABS system warning light, weak braking, and error codes. I took it to my regular workshop where they discovered the brake system was bled incorrectly during a previous service. The hydraulic brakes werent working at full capacity because of trapped air in the system. The fix was relatively straightforward. The mechanic properly bled the brake system and checked the brake booster and pressure sensor connections. Total cost was 90€ and it took about an hour. Before jumping to conclusions about major repairs, could you share: When was your last brake service? Do you hear any unusual sounds when pressing the brake pedal? Does the brake pedal feel spongy or go all the way to the floor? Which error codes specifically show up on the diagnostic tools? This information would help determine if your issue is similar to what I experienced or if its something different.

Thanks for sharing your experience. At last service (124741km) the mechanic also checked my brake performance and found nothing unusual. However, the brake pedal does feel spongy now and makes a slight hissing sound when pressed. The error codes I get are P0503 and C1288. The hydraulic brakes definitely feel different than a month ago, more pressure needed for same braking effect. Since its affecting the ABS system too, I guess just bleeding the brake system might not fix it in my case. Will probably need the pressure sensor replaced. How did you confirm it was just trapped air in your brake system before getting it fixed?

Thanks for those additional details. After seeing your error codes and symptoms, I think your case is different from what I experienced with my VW Polo. In my situation, I confirmed it was trapped air because: No error codes were stored in the ABS system, The spongy feeling improved after pumping the brake pedal a few times, There was no hissing sound Your hissing sound combined with error code C1288 strongly suggests a brake booster pressure sensor issue, which matches your initial suspicion. The P0503 code typically relates to vehicle speed sensor inconsistency, which can trigger when the brake system isnt communicating correctly with the ABS system. My incorrectly bled brake system was a simpler fix. Your symptoms point to a more complex issue affecting multiple brake system components. Based on my experience with VW parts and labor rates, expect: Pressure sensor replacement: 180-250€, Labor time: 2-3 hours, Possible system bleeding and recalibration: 70-100€ Recommend getting this checked soon since compromised brake performance can be dangerous. The diagnostic tools should confirm if its the pressure sensor, but those error codes are pretty telling.

Thanks for the detailed response. Given the error codes and what you described about your experience, I feel more confident now that my initial diagnosis about the pressure sensor was right. The hissing sound seems to be a clear indicator that wasnt present in your case. Your pricing estimate helps me budget for the repair. Since were talking about critical safety components like the hydraulic brakes and ABS system, I wont try to save money by delaying the fix. The diagnostic tools are showing clear warnings, and I dont want to risk having the brakes fail completely. Ill schedule an appointment with my workshop tomorrow. Will ask them to focus on the brake booster pressure sensor first, but also do a full system check including bleeding the brakes just to be thorough. The 300-350€ total cost you mentioned seems reasonable for ensuring the brake pedal works properly again. Thanks again for helping me understand the difference between a simple air bubble issue and what seems to be a genuine sensor failure in my case.