Test Step 2 - THERMOSTAT OPERATION

NOTE:

This test works best if performed on a cold engine (cold soak)

Ignition on, engine not running.
Using the scan tool, read the Engine Coolant Temp Degree value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.

NOTE:

If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached.

Start the Engine.
During engine warm-up monitor the Engine Coolant Temp Degree value. The temp deg value change should be a smooth transition from start up to normal operating temp 82°C (180°F). Also monitor the actual coolant temperature with a thermometer.

NOTE:

As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the scan tool Engine Coolant Temp Degree values should stay relatively close to each other.

Using the appropriate Service Information, determine the proper opening temperature of the thermostat.

Did the thermostat open at the proper temperature?

Yes

Go to Test Step 3 - ECT SENSOR OPERATION

Replace the thermostat. Refer to Removal and Installation .
Perform the Powertrain Verification Test. Refer to PCM Verification Test (2009 - 2011) & PCM Verification Test (2012 & Up) .