DTC P0128: Coolant Thermostat Inoperative: Condition

DTC is set when Engine Control Module (ECM) detects engine coolant temperature is lower than 167°F (75°C), after vehicle has been driven under specified conditions. MIL is illuminated when ECM detects malfunction during 2 consecutive drive cycles. Possible causes are:

• ECM malfunction.
• Engine Coolant Temperature (ECT) sensor malfunction.
• ECT sensor circuit malfunction.
• Thermostat malfunction.