P01F0 code meaning
Coolant Temperature Relapsed Below Diagnostic Monitoring Temperature
Powertrain system Generic code P01xx codes Check engine light
What P01F0 means
Since model years 2019–2021 CARB requires gasoline 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.
P01F0 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P01F0
- Check engine light on (after two drive cycles)
- Temperature gauge drops while driving
- Weak cabin heating, higher consumption
Common causes of P01F0
- Most 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
- Less likelyLow coolant or air in the system
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ThermostatEngine coolant temperature sensorCooling system
What each part of P01F0 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| F0 | The exact fault in that area. |
What to do next
- Note P01F0 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P01F0
What does P01F0 mean?
P01F0 means "Coolant Temperature Relapsed Below Diagnostic Monitoring Temperature". Since model years 2019–2021 CARB requires gasoline 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P01F0?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P01F0 fail an emissions test?
Yes, it can. P01F0 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P01F0 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P01F0 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.