Circuit DescriptionThe fan control circuit is a device used by the engine to control the fan operation. When the electronic control module (ECM) energizes the fan control circuit, the engine fan is engaged.

The fan control circuit utilizes a pulse width modulated (PWM) signal. A PWM signal is a pulsed voltage signal between 0-VDC and system voltage. The frequency of the pulsed voltage signal is dependent on the application requirement.

There are two types of fans supported by the fan control circuit; variable speed and ON/OFF. INSITE? electronic service tool can be used to determine which fan type is presently set up for use. The fan control circuit varies by the OEM. OEMs can use a solenoid return that is wired to the ECM or use a return that goes to engine block or chassis ground.

Component LocationThe control solenoid location varies by OEM. Refer to the appropriate OEM service manual to determine the location.

Conditions for Running the DiagnosticsThis diagnostic runs when the keyswitch is in the ON position and when the pulse width modulated (PWM) device is getting energized or de-energized. In some cases, the diagnostics can also run at certain fixed intervals.

Conditions for Setting the Fault CodesThe fan control circuit pulse width modulated (PWM) signal is not detected to be system voltage when the pulse width modulated (PWM) signal is turned ON.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.The fan will not be enabled.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 lamp after the diagnostic runs and passes.The ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults.

Shop TalkThe fan control logic can be adjusted with INSITE? electronic service tool. There are two choices: 12 or 24 volts ON, or 0 volts ON. For proper fan operation, the fan control logic setup with INSITE? electronic service tool must match the hardware configuration on the vehicle.

This fault code is logged when the ECM commands 12 or 24-VDC to the fan control solenoid, but the voltage on the fan control signal circuit is less than 12 or 24-VDC. The low voltage on the signal circuit usually indicates a short circuit to ground in the harness or solenoid.

If Fault Code 245 is still active after completing the following troubleshooting steps, consult the OEM service manual for procedures to check the fan control circuit for a short circuit to ground.

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink 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) Fan Control Solenoid failure2) OEM harness3) ECM Failure