P26AAEngine Coolant Bypass Valve A Position Sensor Maximum Stop Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P26AA is the upper-limit partner of P26A9: the controller cannot confirm or learn the maximum end stop of valve A, or the reported value at full travel lies outside the expected window. No manufacturer publishes criteria for this code. GM's Volt logic for P26A9 shows how such checks work: the valve is driven to an end, given a fixed time to arrive and relearned several times before a fault is stored. Subaru's bulletin 09-80-21 names the P26A family in general for sensor corrosion on its thermo control valve. CARB expects the OBD system to notice when such an output ignores its commands, wherever a test of its response is feasible. Likely causes are mechanical binding near full open, a damaged stop, or a sensor that saturates early.
- What you may notice
- Check engine light
- Reduced cooling under high load
- Heater or engine temperature not as expected
- Likely causes
- LikelyValve binding before reaching its maximum position
- PossibleWorn or broken mechanical end stop or gear
- RarePosition sensor out of calibration near its upper end
- 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: €0 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.