P26B1Engine Coolant Bypass Valve A Stuck Closed
- 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
- P26B1 reports that valve A does not open when it should. The best documented user is the Volkswagen group plug-in hybrids. Porsche stores P26B100 in the thermal management unit (TME) of the 2019–2022 Cayenne E-Hybrid and the 2019–2021 Panamera E-Hybrid for the valve that admits engine coolant to the heating circuit once the engine passes 40 °C. The TME infers its state from the gap between two coolant temperatures, with 7 °C as the limit, and certain conditions caused false entries; bulletins 116/22 and 193/22 reprogram the TME. Bentley found the same code on 2022 Flying Spur Hybrids (N91 valve) and also fixes it by software. A real fault leaves the heating circuit without engine heat and can affect warm-up strategy.
- What you may notice
- Check engine light, sometimes only intermittent
- Cabin heat relies on the electric heater longer than usual
- Possible rise in engine temperature under load
- Likely causes
- LikelyThermal management software misjudging the valve (Porsche, Bentley)
- PossibleValve seized closed by deposits or a failed actuator
- RareSwapped or kinked coolant lines after repair
- RareDrifting coolant temperature sensor used for the check
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · 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.