Powertrain, generic (extended)

P2CBA Fan 2 Overspeed

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

With P2CBA the controller finds fan 2 spinning clearly faster than its own estimate of what the current command should produce. GM documents the check in tables 23OBDG07 and 24OBDG07: the reported speed minus the estimated speed must exceed a margin of 1400 to 4050 rpm, depending on the operating point, for 20 s with more than 9.5 V on board, and the lamp follows on the second trip. A separate GM code covers readings beyond 4999 rpm that cannot be real, so P2CBA points to a fan that really turns too fast or a motor controller that ignores its command. Typical reasons are a broken or missing blade section, a damaged shroud letting the rotor run free, or a fan module that drives at full power. GM's 2025 diesel table does not use P2CBA. Underspeed of the same fan is P2CB9, fan 1 overspeed P0495.

Likely causes

Fan blade broken or partly missing, less load on the motor
Fan electronics drive the motor harder than commanded
Implausible speed feedback from the fan module
Shroud damaged or detached so the rotor runs free

Symptoms

  • Check engine light after two trips
  • Unusually loud or vibrating fan noise
  • Fan runs at high speed even with a cool engine

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–900
Time0.5–4 h

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

Parts involved

cooling fan 2

Related codes

P2CB9P0495P2CBCU0633P2B32

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.