Circuit DescriptionThe engine control module (ECM) supplies a 5 volt supply to the engine coolant level sensor using a common sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The engine coolant level sensor provides a signal to the ECM on the engine coolant level sensor signal circuit. This sensor signal voltage changes based on the coolant level in the expansion tank.

Component LocationThe engine coolant level sensor is typically located in the radiator top tank or surge tank. Refer to the OEM service manual for component location.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position, or when the engine is operating.

Conditions for Setting the Fault CodesThe ECM detects that the coolant level signal voltage is greater than a calibratible value for more than 1 second.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.No engine protection will be available for low coolant level.Conditions for Clearing the Fault CodeTo validate the repair, start the engine and let it idle for 1 minute.The fault code status displayed by INSITE? electronic service tool will change to inactive immediately after the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE light after the diagnostic runs and passes.For On-Board Diagnostics (OBD) engines, the ECM will turn off the malfunction indicator lamp (MIL) after three consecutive trips where the diagnostic runs and passes.The “Reset All Faults” command in INSITE? electronic service tool can be used to clear active and inactive fault codes, as well as extinguish the MIL for OBD engines.

Shop TalkPossible causes of this fault code include:

Open return circuit in the engine harness, connectors, or sensorSignal circuit shorted to sensor supply or battery voltageSensor supply circuit shorted to battery voltage.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and data link communication issues with aftertreatment components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing, or intermittent connections.

Possible Cause:1) OEM harness2) ECM calibration