P2B5FEngine Coolant Flow Control Valve Position Sensor Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2B5F is set when the valve position signal sits above the top of its window. The 2025 Duramax calibration (3.0 L, 25OBDG04B) treats a SENT raw value over 98 % of 5 V as implausibly high and stores a two-trip Type B code after 80 of 100 readings, sampled every 6.25 ms while the SENT link itself is healthy. A signal shorted to the 5 V reference or to supply, a moisture path in the connector or an internal sensor fault are the usual explanations; GM's 21-NA-149 lists P2B5F with the LM2 harness-chafing codes as well. Coolant flow control switches to a fallback, which can show as slow warm-up or weak cabin heat. Low counterpart: P2B5E.
- What you may notice
- MIL on after two drives
- Slow warm-up or weak cabin heat
- Likely causes
- LikelySignal wire shorted to the 5 V reference or to battery voltage
- PossibleMoisture or corrosion bridging contacts in the valve connector
- RarePosition sensor in the valve faulty
- 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: €50 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.