Powertrain, generic (extended)

P2CB2 Charge Air Cooler Coolant Pump B Underspeed

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

With P2CB2 the speed reported by charge air cooler pump B stays below what it should reach. The motor is braked mechanically or gets too little power: a dragging bearing, debris or sludge at the impeller, a weak supply or a high-resistance connector. No manufacturer documents P2CB2 publicly. GM's pump A version, P2B84 in table 25OBDG04B, trips on a reported speed below −115 rpm, effectively a stopped or backward-turning rotor, in 8 of 10 samples with at least 11 V, Type B. GM bulletin 23-NA-102 traced such pump faults on the 3.0-litre Duramax to water getting into the plug of pump M10, a reminder to inspect the connector first. Less flow means warmer charge air and possible power loss. A rotor that cannot move at all is P2CB3.

Likely causes

Dragging bearing or sludge slowing the rotor of pump B
Water or corrosion in the pump connector raising resistance
Low supply voltage from a poor ground or weak battery

Symptoms

  • MIL on after two trips
  • Charge air runs hot, engine power reduced under load

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–800
Time0.5–3 h

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

Parts involved

cac coolant pump bwiring harnessecm

Related codes

P2B84P2CB1P2CB3P2CB0P2CB4

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