Powertrain, generic (extended)

P2B84 Charge Air Cooler Coolant Pump A Underspeed

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Worn or seized pump bearing, or debris blocking the impeller
Water or corrosion in the pump connector
Low supply voltage or poor ground at the pump
Pump motor or its electronics worn out

Symptoms

  • Check engine light after the second faulty drive
  • Less power under heavy load or when towing
  • High charge air temperature shown in live data

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–900
Time1–3 h

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

Parts involved

cac coolant pump acac coolant loop

Related codes

P2B83P026EP2BC1P2CB2P2BC2

References: gsi.ext.gm.com, static.nhtsa.gov, law.cornell.edu.