OBD-II code · Chassis
C05AC Brake Blending Separation Valve Stuck Closed
Brake blending separation valve stuck closed — regen and hydraulic circuits cannot be isolated.
Is it safe to drive with C05AC?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyValve stuck closed
- Less likelyCarbon or debris buildup preventing free movement
- Less likelyComponent wear with age - mechanical play
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
- 2–6 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Brake Blending Valve
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.