| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuits are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Circuit Description
DTC is set when ECM detects coolant temperature is less than 167°F (75°C) when engine should be at normal operating temperature. Possible causes are
- Defective thermostat.
- Defective cooling system.
- Defective engine coolant temperature sensor.
- Defective ECM.
Diagnostic Aids
Using scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.