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.
How the engine computer detects it
P01F0 is this check. GM sets it when coolant falls below 64 °C (147 °F) with a conventional thermostat or 70.5 °C (159 °F) with an electrically heated one (2019 Corvette: 65/78.5 °C (173 °F)) after having been above it, with at least 0.8 km driven, ambient above −7 °C (19 °F), enough heat input and no long overrun downhill; two trips. GM also uses it on the 6.6 liter 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.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on (after two drive cycles)
- Temperature gauge drops while driving
- Weak cabin heating, higher consumption
Common causes
- Thermostat stuck open or not sealing Most likely
- Heated map thermostat, thermal management valve or switchable water pump faulty Possible
- Radiator fan running constantly (relay stuck) Possible
- Coolant sensor drifting cold Possible
- Low coolant or air in the system Less likely
How to diagnose P01F0
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: thermostat, engine coolant temperature sensor, cooling system.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P01F0 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Chevrolet Blazer | 2020 | 3 | — | |
| GMC Acadia | 2020 | 3 | — |
Counts of owner complaints to the NHTSA that mention P01F0 (7 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 1
- Fuel and air metering
- F0
- Specific fault
Questions drivers ask
Can I drive with code P01F0?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P01F0?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P01F0 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P01F0 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
Often reported together
Codes that owners mention in the same NHTSA complaints as P01F0. They can point to a shared cause, so it's worth checking them together.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.