P26A4Engine Coolant Bypass Valve A Position Sensor Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Many electric coolant valves carry a potentiometer or Hall element that reports the actual valve angle back to the controller. P26A4 is the general circuit code for that feedback on valve A: the signal is missing or cannot be assigned to a more specific low, high or erratic fault. No manufacturer documents P26A4 itself in public. GM's Volt tables cover the same sensor only through P26A6/P26A7, and Subaru bulletin 09-80-21 (Forester, Outback, Legacy, Crosstrek 2019–2021) mentions P26A-series codes in general when water reaches the sensor portion of the thermo control valve. CARB requires input signals to be checked for continuity. Without valid feedback the controller loses track of the valve, so warm-up and cooling may run on a fallback setting.
- What you may notice
- Check engine light
- Slow warm-up or weak cabin heat
- Possible additional valve or coolant temperature codes
- Likely causes
- LikelyMoisture or corrosion inside the valve's position sensor section
- PossibleLoose, corroded or damaged connector or feedback wiring
- RareMissing 5 V reference or ground for the position sensor
- 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 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.