What does code P0128 mean?
P0128 means the engine has not reached its normal temperature in the time it should. Often the thermostat is stuck open, so coolant keeps flowing through the radiator and staying cool.
Why does code P0128 appear?
- The thermostat is stuck open.
- The coolant level is low.
- The coolant temperature sensor is reading wrong.
- The radiator fan runs all the time.
What can you safely check for P0128?
- Notice whether the temperature needle stays low even after 10 to 15 minutes of driving, and whether the heater blows cold air in winter.
- Only when the engine is cold, check the coolant level in the see-through reservoir tank. Don't remove the radiator cap.
Is it safe to drive with P0128?
You can usually keep driving, but fuel use goes up and the heater stays weak in winter. If the temperature needle climbs towards red, stop somewhere safe straight away and switch off the engine.
Safety: never remove the radiator cap on a hot engine; boiling coolant can burn you. Keep your hands away from the fan and belts while the engine runs. If you smell fuel, switch off, keep any flame or cigarette away and call a mechanic.
When should you call a mechanic?
Replacing the thermostat means draining and refilling the coolant, so have a car mechanic (mistri) do it. They will also test the sensor so the right part is replaced.