P2CB1Charge Air Cooler Coolant Pump B Overspeed/Air In System
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2CB1 means pump B in the charge air cooling loop turns faster than it should. An electric pump loses its hydraulic load when the impeller churns air instead of coolant, so overspeed is mostly a symptom of a low level or poor bleeding. No manufacturer documents P2CB1 publicly. For pump A (P2B83), GM's 2025 diesel table 25OBDG04B treats 8,500 rpm or more in 8 of 10 one-second samples as a fault, at 11 V or higher, Type B with MIL after two trips. GM's LT4 bulletin 18-NA-291 adds that this kind of pump shuts itself off once it draws air, which is why the loop there has to be vacuum filled. Check level, leaks that suck in air, and the bleed procedure before replacing pump B. If the pump then overheats, P2CB5 may follow.
- What you may notice
- MIL on after two trips
- Gurgling or a high-pitched pump noise
- Low coolant warning or falling expansion tank level
- Likely causes
- LikelyAir trapped in the loop after service or incomplete bleeding
- LikelyLow coolant from a leak in the charge air cooler circuit
- RareImpeller loose or broken on the shaft of pump B
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.