What usually causes it
- A thermostat stuck open
- A failing coolant temperature sensor
- Low coolant
- A cooling fan that runs all the time
P0128Starts at: OK to drive, fix when convenient
Engine is not reaching normal temperature (thermostat)
The coolant stays cooler than it should after you drive for a while. The thermostat, the valve that holds heat in the engine, is often stuck open.
Check this first
Only when the engine is fully cool, look at the coolant level in the plastic tank. Never open the radiator cap on a hot engine.
What to watch for
- The heater blowing weak or cold air in winter
- The temperature gauge never reaching the middle
- The gauge suddenly shooting into the hot zone
Can I keep driving?
We rate P0128 as OK to drive, fix when convenient, as a starting point. Keep an eye on the signs below. If the light starts flashing, stop driving soon.
Quick answers about P0128
What does P0128 mean?
Engine is not reaching normal temperature (thermostat). The coolant stays cooler than it should after you drive for a while. The thermostat, the valve that holds heat in the engine, is often stuck open.
Can I keep driving with P0128?
We rate P0128 as OK to drive, fix when convenient, as a starting point. Keep an eye on the signs below. If the light starts flashing, stop driving soon.
What usually causes P0128?
The most common causes, in order: A thermostat stuck open; A failing coolant temperature sensor; Low coolant; A cooling fan that runs all the time.
Estimates only. A mechanic should confirm. The same code can mean slightly different things on different cars; the app explains it for your exact year, make, model and mileage.