P26ABEngine Coolant Bypass Valve A Stuck/Open
- 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
- P26AB is stored when valve A stays open although it was told to close. Ford's hybrid summaries (2014–2019) define the valve as the switch between a combined loop, with engine coolant through the heater core, and an isolated loop heated by a PTC heater; if the second coolant sensor reads more than 5 °F above the engine sensor within 60 s of a circuit fault, the valve is judged stuck in the combined loop, and P2682 must set first. On 2016–2017 smart fortwo cars a corroding vacuum change-over valve keeps the heater shut-off valve open, so Mercedes-Benz extended its warranty to 10 years. Ram 1500 trucks of 2013–2015 (3.6, 4.7 and 5.7 L) and 3.0 L diesels received PCM flashes that list P26AB.
- What you may notice
- Check engine light
- Engine takes long to warm up, higher fuel use when cold
- Heater works with engine off only poorly (hybrids)
- Likely causes
- LikelyValve jammed open by deposits, wear or a broken drive part
- PossibleCorroded vacuum change-over valve (smart fortwo 453)
- PossibleEngine control software misjudging valve state (Ram flashes)
- RareDrive circuit fault leaving the valve in its open default
- 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 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.