C05ABBrake Blending Separation Valve Performance
- Generic OBD-II code · Chassis
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- C05AB concerns the separation valve that decouples the driver's master cylinder from the wheel circuits while the brakes work by wire, so that pedal pressure does not cut into regenerative braking. It is usually open without current, so the pedal acts on the wheels if power fails, as in Continental's brake-by-wire layout. A performance fault means it does not seal or switch as expected. Mando's patent shows how a leak is found: if pedal simulator pressure follows circuit pressure too closely, fluid is getting through; the valve is re-energised to free a stuck seat, and after repeated failures the system warns and returns to direct pedal braking, as leaking pressure can kick back into the pedal. Toyota patents isolate a valve by response delays. No manufacturer publishes C05AB.
- What you may notice
- Pedal kickback or vibration during braking
- Regenerative braking reduced, brake warning message
- Brakes switch to direct pedal operation with higher effort
- Likely causes
- LikelyDirt or debris on the valve seat causing leakage
- PossibleValve coil or its driver in the module not switching properly
- PossibleOld or wrong brake fluid making the valve sluggish
- RarePressure sensor errors making the valve look faulty
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.