Engine Thermostat Testing

All models are equipped with On-Board Diagnostics for certain cooling system components. Refer to Powertrain Management, On-Board Diagnostics (OBD) for additional information. If the Powertrain Control Module (PCM) detects low engine coolant temperature, it may record a Diagnostic Trouble Code (DTC) in the PCM memory. Do not change a thermostat for lack of heat as indicated by the instrument panel gauge or heater performance unless a DTC is present. Refer to individual component testing and inspection for other probable causes. For other DTC numbers, refer to On-Board Diagnostics in Powertrain Management.
The DTC can also be accessed through the DRB scan tool. Refer to Powertrain Management for the appropriate Powertrain Diagnostic Procedures information and operation of the DRB scan tool.