Circuit Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
An engine coolant temperature (ECT) sensor monitors the temperature of the coolant. The fuel burned since start up is 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 engine coolant temperature as enabling criteria, may not run when expected.
This DTC will only run once per ignition cycle until a Pass, Fail or Disable condition exists.
If the engine coolant fails to reach a preset target temperature before the calculated amount of fuel is burned, DTC P0128 will set.