Thermostat: Testing and Inspection

ON-BOARD DIAGNOSTICS (OBD)

All engines are equipped with On-Board Diagnostics (OBD) for certain cooling system components. If the powertrain control module (PCM) detects low engine coolant temperature, it will 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 by poor heater performance unless a DTC is present. Testing and Inspection for other probable causes.