P2C66Hybrid/EV Electronics Coolant Pump A Underspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2C66 reports that pump A of the electronics cooling loop, which carries heat away from inverter, DC/DC converter and often the on-board charger or drive motor, turns slower than requested. Pumps of this kind report their actual speed, and the controller compares it with the target. No manufacturer publicly documents P2C66. Ford's 2024 summary uses the same fault type, under-speed (B2), for engine coolant pump A, monitored continuously over 5 seconds above 11 V. GM's 2016 Volt judges pump A of its power electronics loop differently, as P0CEA, when coolant and charger temperatures drift apart. Worn bearings, sludge or debris, low supply voltage and partial air are typical. Expect reduced drive power or slower charging. Overspeed is P2C67, a stalled pump P2C68.
- What you may notice
- Hybrid/EV system warning and check engine light
- Reduced drive power or slower charging
- Electronics temperature rises faster than usual
- Likely causes
- LikelyWorn bearings or a sluggish impeller
- PossibleDebris or sludge in the pump or a restricted loop
- PossibleLow supply voltage from fuse, relay or ground faults
- RareAir pockets after a coolant service
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.