P2B5AEngine Coolant Flow Control Valve Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2B5A stands for a short to ground in the control wiring of the coolant flow control valve motor. GM's 2025 table for the 3.0-litre Duramax describes the detection: the driver sees more than 9 A flowing, which it interprets as one motor wire touching ground, and 80 out of 100 samples at 12.5 ms set a two-trip Type B fault once relay voltage exceeds 11 V. Unlike P2B58, where the motor itself draws too much current, the cause here is normally insulation damage in the harness, a pinched wire near the valve or water in the connector. The valve stays in its last or default position, so coolant distribution becomes fixed. Short to power is P2B5B, open circuit P2B59.
- What you may notice
- MIL on after two drives
- Engine temperature control fixed, slower warm-up or higher running temperature
- Likely causes
- LikelyMotor wire chafed or pinched against ground
- PossibleCoolant or water in the valve connector
- RareInternal short to housing in the valve motor
- 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: €60 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.