Powertrain, generic (extended)

P2ACB Charge Air Cooler Coolant Temperature Sensor B Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2ACB covers a sensor B signal that jumps or briefly drops out instead of following the slow temperature changes of a coolant loop. The title, without the word circuit, also includes erratic values while the wiring stays intact. No maker publishes the B-side check. GM's 2025 diesel table shows how the A-side version (P00E2) works: it builds moving limits around the last good reading using the sensor's filter time and counts 60 failed samples out of 75 against them, Type B. A test of this kind only runs while no steady circuit fault is present, so P2AC9 or P2ACA take priority. Typical causes are a terminal with poor contact tension, a connector loosened by vibration or coolant that has crept into the plug. Wiggle the harness while watching live data.

Likely causes

Terminal with weak contact tension in the sensor B plug
Harness rubbing through intermittently under vibration
Coolant crept into the connector
Sensor B element with unstable output

Symptoms

  • Check engine light comes and goes
  • Sensor B value jumps in live data

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–300
Time0.5–2 h

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

Parts involved

charge air cooler coolant temp sensor bwiring harness

Related codes

P2AC7P2AC8P2AC9P2ACAP00E2

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