OBD Engine Coolant Bypass Valve B Position Sensor Circuit High
What it means
P2AAA stands for Engine Coolant Bypass Valve B Position Sensor Circuit High. P2AAA is a P code, so the fault sits in the engine, transmission and emissions systems. For P2AAA, work through the cause list below, cheapest checks first.
Where it lives
For P2AAA, the description names the sensor as the part involved.
What to check first
For P2AAA, clear the code, drive a short distance and read it again, since a code that comes back is still there and one that does not was history.
Check these first
- P2AAA: Faulty or contaminated sensor in the fuel/air metering circuit
- P2AAA: Damaged or shorted wiring or connector for the affected circuit
- P2AAA: Vacuum leak or intake system restriction
- P2AAA: Failing fuel pump, injector, or fuel pressure regulator
What to do next
P2AAA reports from the powertrain control system. These steps cover P2AAA in general, and the exact cause on your vehicle can differ from the cause named above.
- P2AAA: Read freeze frame data and related codes with an OBD-II scanner
- P2AAA: Inspect the affected sensor wiring and connector for damage
- P2AAA: Compare live sensor readings (fuel trim, airflow, temperatures) to manufacturer specs
- P2AAA: Smoke test the intake system if lean or vacuum conditions are suspected
- P2AAA: Replace the failed component after confirming it with live data
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.