Coolant Thermostat Below Regulating Temperature
| Code | P0128 |
| Description | Coolant Thermostat Below Regulating Temperature |
| Possible Causes | The thermostat is not reaching its designed operating temperature. Common cause: stuck-open thermostat. |
| System | Fuel and Air Metering |
Coolant Thermostat Below Regulating Temperature. This diagnostic trouble code (DTC) is stored when the vehicle's onboard computer detects an issue with the fuel and air metering.
P = Powertrain code
0 = Generic (SAE standard)