Powertrain, generic (extended)

P26FA Coolant Pump C Overspeed/Air in System

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Low coolant level or air left in the low-temperature loop after service
Leak in the loop drawing in air
Chafed engine harness corrupting pump signals
Impeller slipping on its shaft or broken

Symptoms

  • Check engine light on after two trips
  • Gurgling from the pump area
  • Higher charge air temperature and possibly reduced power

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–400
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant pump ccooling systemcoolant reservoir

Related codes

P2BA0P26F8P2C48P26CE

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.