Powertrain, generic (extended)

P2AC8 Charge Air Cooler Coolant Temperature Sensor B Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2AC8 sets when charge air cooler coolant temperature sensor B delivers an electrically valid value that makes no sense for the situation, for example after a long engine-off period when every temperature in the engine bay should have converged, or when it fails to change while the loop pump runs and the cooler heats up. No maker documents this exact check publicly; Ford and GM only publish thresholds for sensor A (P00DE to P00E2). Besides a drifting sensor, the low-temperature circuit itself can trigger it: low coolant, trapped air or a weak electric pump make the reading real but unexpected. Check level and bleeding first, then compare B in live data with sensor A and with the engine's own coolant reading. Hard limits of the signal are P2AC9 and P2ACA.

Likely causes

Low coolant level or air trapped in the low-temperature loop
Sensor B drifting out of its characteristic
Electric charge air cooler coolant pump weak or not running
Control module software needing an update

Symptoms

  • Check engine light on, often only after several drives
  • Sensor B reads clearly different from sensor A after a cold soak
  • Higher intake air temperature under load

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–450
Time0.5–2.5 h

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

Parts involved

charge air cooler coolant temp sensor bcharge air cooler coolant pumplow temperature coolant circuit

Related codes

P2AC7P2AC9P2ACAP2ACBP00DF

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