P2B84Charge Air Cooler 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
- P2B84 reports that the electric charge air cooler pump is turning too slowly or not at all, judged by the speed its own electronics send back. GM lists the code next to P2B83 in the 2025 diesel table 25OBDG04B as the low out-of-range case of the pump speed, with the limit printed as a reading below -115 rpm; 8 failed one-second samples out of 10 are needed, with the pump fitted and enabled, relay voltage at 11 V or more and the engine not cranking. Type B, so the MIL comes on after the second faulty trip. Typical reasons are a seized bearing, debris at the impeller, a weak supply or a corroded connector – GM's bulletin 23-NA-102 found water entering the M10 pump plug on the 3.0-litre Duramax. With little flow the intake air runs hot.
- What you may notice
- Check engine light after the second faulty drive
- Less power under heavy load or when towing
- High charge air temperature shown in live data
- Likely causes
- LikelyWorn or seized pump bearing, or debris blocking the impeller
- PossibleWater or corrosion in the pump connector
- PossibleLow supply voltage or poor ground at the pump
- RarePump motor or its electronics worn out
- 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: €150 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.