Brake Booster Fault Code C1187F6 ?

[Audicfc]

Just bought a used approved 2023 audi s3 and scanned the car a few times since I got it few days and the one that keeps coming back is ;

brake booster - functional limitation of external brake pressure build up with fault code C1187F6

Does anyone know what the problem is and would this be covered under warranty even though theres no warning lights on the dashboard it is only showing up when I scan it with obdeleven

 

[Vic20]

Gemini says... Check the plug as yours is likely very transient/intermittent
/ an easy fix

Fault code C1187F6 indicates a function restriction of external brake pressure build-up, typically caused by a faulty brake booster pressure sensor (G294) in VAG (Audi/VW) vehicles. This triggers limited hydraulic brake assist (HBC) and causes "brake servo restricted" warnings. Driving should be limited to avoid overloading the ABS module.


Key Implications and Details:

System Impact: The ABS/ESP module (specifically Bosch ESP9) cannot generate sufficient brake pressure via the electronic booster when needed.

Symptoms: "Brake Servo Restricted" warning light, potentially accompanied by start-stop issues.

Causes: Faulty brake booster pressure sensor (often 2018–2021 models), low voltage, or sensor wiring issues.

Repair Action: The sensor (G294) is usually located near the master cylinder on the vacuum line. Replacing it is a 5–10 minute job, often plugging into the vacuum pipe.

Warning: Continued driving with this fault can damage the ABS pump, leading to expensive repairs (roughly £3,000).

Recommendation: Use original OEM sensors to avoid premature failure.



Note: For diagnosis, check the live data of the brake pressure sensor and monitor for related low-voltage codes (e.g., C118816).

 

[ptf]

I would ask dealer to fix, especially if the car has some of the original 3-year warranty left to run.

However easy the fix if you repair it yourself and it comes back again after the warranty runs out then you are a bit stuck. If repaired under warranty and the fault recurs you can reasonably ask that any subsequent sort out for the same fault is done at Audi's expense.