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Cummins ISX11.9 CM2250 (2010-12) Fault Code: 2377 PID: SID 33 SPN: 647 FMI: 3 Fan Control Circuit- Voltage Above Normal or Shorted to High Source

Circuit Description
The 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 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 Location
The fan clutch solenoid location varies by OEM. Refer to the OEM service manual.

Conditions for Running the Diagnostics
For ON/OFF and variable speed fan types, the diagnostic runs when the fan is turned off and will latch active when the fan PWM signal is 100 percent. For all other fan types, the diagnostic runs when the fan PWM signal is less than 100 percent and will latch active when the fan PWM signal is 100 percent.

Conditions for Setting the Fault Codes
The fan control circuit PWM signal is detected to be greater than 0-VDC when the PWM signal is turned off by the ECM.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
Fan operation will be disabled.
Conditions for Clearing the Fault Code
To validate the repair, perform a key cycle and leave the key in the ON position for 1 minute.
The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes. For ON/OFF and variable speed fans, the diagnostic runs when the fan is turned OFF. For all other fan types, the diagnostic runs when the fan PWM signal is less than 100 percent.
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 Talk
If Fault Code 2377 is still active after completing all the steps in this fault code troubleshooting tree, consult the OEM service literature for procedures to check the fan clutch device for an open circuit or short circuit to ground.

Possible causes of this fault include:

An open circuit in the engine harness or fan control solenoid.
A short circuit to voltage source in the OEM harness.
A malfunctioning ECM.
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 failure
2) OEM harness
3) ECM failure