P26FACoolant Pump C Overspeed/Air in System
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P26FA flags a coolant pump C that turns far faster than it should – the classic sign of a pump moving air instead of liquid. GM uses the code in the engine module of its diesel calibrations for the pump of the low-temperature coolant loop: in table 20OBDG04 an actual speed of at least 4,500 rpm in 5 of 8 one-second samples sets it, in 25OBDG04A 4 of 5 samples suffice. Both list it as Type B, so the MIL comes on after two trips; the test needs at least 11 V at the powertrain relay and is skipped while the engine cranks. GM bulletin 21-NA-149 names P26FA among many codes caused by a chafed engine harness on Silverado and Escalade models. The first check is coolant level and bleeding; the sister codes P2BA0 (underspeed) and P26F8 (stuck) cover the opposite cases.
- What you may notice
- Check engine light on after two trips
- Gurgling from the pump area
- Higher charge air temperature and possibly reduced power
- Likely causes
- LikelyLow coolant level or air left in the low-temperature loop after service
- PossibleLeak in the loop drawing in air
- RareChafed engine harness corrupting pump signals
- RareImpeller slipping on its shaft or broken
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.