P01F0Coolant Temperature Relapsed Below Diagnostic Monitoring Temperature
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Since model years 2019–2021 CARB requires petrol engines to detect a thermostat fault not only during warm-up but also when the coolant, after reaching operating temperature, drops back below the temperature needed for other diagnostics. P01F0 is this check. GM sets it when coolant falls below 64 °C with a conventional thermostat or 70.5 °C with an electrically heated one (2019 Corvette: 65/78.5 °C) after having been above it, with at least 0.8 km driven, ambient above −7 °C, enough heat input and no long overrun downhill; two trips. GM also uses it on the 6.6 litre Duramax diesel as a 'stuck open thermostat' check. Ford does not use the code in the documents checked. Usual cause is a thermostat stuck open.
- What you may notice
- Check engine light on (after two drive cycles)
- Temperature gauge drops while driving
- Weak cabin heating, higher consumption
- Likely causes
- LikelyThermostat stuck open or not sealing
- PossibleHeated map thermostat, thermal management valve or switchable water pump faulty
- PossibleRadiator fan running constantly (relay stuck)
- PossibleCoolant sensor drifting cold
- RareLow coolant or air in the system
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.