Circuit DescriptionThe fan control circuit is a device used by the engine to control the fan operation. When the engine 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 requirements.

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 currently set up for use. The fan control circuit varies by original equipment manufacturer (OEM). Certain OEMs can use a solenoid return that is wired to the ECM or can use a return that goes to the engine block or chassis ground.

Component LocationThe control solenoid location varies by OEM. Refer to the appropriate equipment manufacturer service information 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 some fixed intervals.

Conditions for Setting the Fault CodesThe ECM detected the fan control circuit PWM signal was not at system voltage when the PWM signal was commanded ON.

Action Taken When the Fault Code is ActiveThe ECM logs the fault code immediately when the diagnostic runs and fails.Fan operation will be disabled.Conditions for Clearing the Fault CodeTo validate the repair, perform a key cycle, 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 Reset All Faults command in INSITE? electronic service tool can be used to clear active and inactive faults, as well as extinguish the malfunction indicator lamp for on-board diagnostics applications.

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 6264 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.

Possible Cause:1) Fan Control Solenoid Failure2) OEM harness3) ECM calibration