Powertrain, generic (extended)

P2B83 Charge Air Cooler Coolant Pump A Overspeed/Air In System

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2B83 concerns the electric pump that keeps coolant moving through a water-cooled charge air cooler. When the impeller runs in air instead of liquid, load vanishes and the motor spins up. GM documents this in its 2025 diesel table 25OBDG04B: a reported pump speed of 8,500 rpm or more in 8 of 10 one-second samples sets the code, provided the pump is fitted and enabled, the engine is not cranking and relay voltage is at least 11 V; Type B, MIL after two trips. GM's 3.0-litre Duramax uses such a pump (M10, bulletin 23-NA-102). GM's bulletin 18-NA-291 for the supercharged LT4 notes that this pump switches off once it draws air, so the loop must be vacuum filled. Too little speed is P2B84, the B pump has P2CB1. Hot charge air can cut power.

Likely causes

Air pocket in the charge air cooler loop after service or a leak
Low coolant level in the separate low-temperature loop
Impeller loose or broken on the pump shaft
Pump electronics reporting an implausible speed

Symptoms

  • Check engine light after two drives with the fault
  • Reduced power under load because the intake air gets hot
  • Falling level in the charge air cooler coolant reservoir

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–800
Time0.5–3 h

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

Parts involved

cac coolant pump acac coolant loop

Related codes

P2B84P026EP2BC1P2CB1P023A

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