P26BCEngine Coolant Bypass Valve C Stuck Closed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P26BC covers a valve C that will not open on command even though its drive circuit is intact. Public criteria for this code are not available from any manufacturer. GM folds a valve C that fails to reach its target into the range/performance code P26BB, and Ford checks its radiator bypass valve C only for circuit faults. GM's stuck-closed logic for the block valve under P26C2 shows one way to detect it: a position error of at least 10° (5° in 2025) while the feedback stays below 50°. CARB asks for functional monitoring of outputs where feasible and for cooling system checks. This is the riskier direction: if valve C blocks flow to the radiator, heat cannot be shed, so watch the temperature gauge and stop before the engine overheats.
- What you may notice
- Check engine light
- Rising engine temperature, possible overheat warning
- Reduced engine power to protect the engine
- Likely causes
- LikelyValve C seized in the closed position
- PossibleActuator too weak to overcome friction or deposits
- RareLow coolant level or trapped air distorting the temperature check
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.