P26B9Engine Coolant Bypass Valve C Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P26B9 reports supply voltage where the valve C driver should see none, in practice a short to battery positive. Two makers document it. Ford's 2024–2025 gasoline summary pairs it with the open-circuit code as P26B9/P26B7_12: the smart driver for the radiator bypass valve flags the fault and the PCM stores it after 5 s of continuous monitoring. The 2020–2023 edition did not yet list a high code. GM's 2025 diesel table 25OBDG04B watches both motor directions of the H-bridge for a line shorted to positive, Type B, and GM bulletin 21-NA-149 names P26B9 among the codes a chafed engine harness can cause. A shorted line may force the motor against an end stop or make the driver shut down, so cooling control is degraded until the wire is repaired.
- What you may notice
- Check engine light
- Temperature gauge higher or more erratic than usual
- Valve does not respond to scan tool commands
- Likely causes
- LikelyDrive wire shorted to a battery-voltage circuit
- PossibleEngine harness damaged by chafing or heat
- RareInternal fault in the valve C actuator
- 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: €60 – €650
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.