OBD-II code · Chassis
C0091 Hydraulic Brake Pressure Sensor Circuit Range/Performance
The brake pressure sensor signal is outside the plausibility band relative to pedal application. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Is it safe to drive with C0091?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelySensor drift with age
- Less likelyInternal hydraulic block leak
- Less likelySensor element aged beyond calibration window
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–4 h
- Emissions test
- Usually unaffected
- Parts involved
- Brake Pressure Sensor, ABS Control Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.