An ECT sensor monitors the temperature of the coolant. This input is used by the control module for engine control and as an enabling criteria for some diagnostics. The air flow coming into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat, the diagnostics that use ECT as enabling criteria may not run when expected. If the control module detects the calibrated amount of air flow and engine run time have been met and the ECT has not met the minimum thermostat regulating temperature, DTC P0128 sets.
Conditions for Running the DTC
P0116
- DTCs P0112, P0113, P0117, P0118, P0601, P0602, P0603, P0604, P0606, P0607, P062F, P2610 are not set.
- The ignition is ON.
- The IAT Sensor parameter is more than 15°C (59°F).
- The Fuel Level Sensor parameter is more than 10 percent.
- The vehicle has a minimum ignition OFF time of 8 hours.
- This diagnostic runs once per ignition cycle when the above conditions are met.
P0128
- DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118 are not present.
- The startup ECT is less than 75°C (167°F).
- The intake air temperature (IAT) is more than -7°C (+19°F).
- The engine run time is between 30-1,800 seconds.
- The vehicle is driven more than 0.8 kilometers (0.5 miles) at more than 8 km/h (5 mph).
- This diagnostic runs once per ignition cycle when the above conditions are met.