P2AABEngine Coolant Bypass Valve B Position Sensor Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2AAB covers a position signal from coolant valve B that is valid most of the time but drops out, jumps or flickers for short moments. Such patterns usually come from a contact that opens under vibration or heat, a lead that rubs against hot engine parts, or interference on the digital sensor line. No manufacturer documents P2AAB publicly, and GM's 2025 diesel tables contain no separate erratic code for the comparable valve C. There, brief disturbances would only surface indirectly, for example as the position deviation code P26BB (more than 12 degrees off target in 8 of 10 seconds) or as the end-stop learn fault P1098 checked after shutdown. CARB asks for circuit and plausibility checks on such inputs. Steady faults are P2AA9 and P2AAA; P2AA7 is the general circuit code.
- What you may notice
- Check engine light that comes and goes
- Occasional temperature swings without a steady pattern
- Often no noticeable change in driving behaviour
- Likely causes
- LikelyWidened or loose terminal in the valve connector
- PossibleHarness rubbing on hot or moving engine parts
- RareElectrical interference or poor ground on the sensor line
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €40 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.