CM850 Electronic Control System – FAULT CODE 2377

Fan Control Circuit – Voltage Above Normal or Shorted to High Source


Fault Code: 2377
PID: S033
SPN: 647
FMI: 3
LAMP: Amber

Fan Control Circuit – Voltage Above Normal or Shorted to High Source. Open circuit or high voltage detected at the fan control circuit.

The fan may stay on continuously or not run at all.

Fan Control Circuit

Circuit Description

The electronic control module (ECM) provides a signal to the fan control solenoid to turn the engine fan on and off. There are two types of fans supported by this signal, variable speed and ON/OFF. The INSITE™ electronic service tool can be used to determine which fan type is currently set up for use. The fan control circuit varies by OEM. Certain OEMs may use a solenoid return that is wired to the ECM or may use a return that goes to engine block or chassis ground.

Component Location

The fan clutch solenoid location varies by OEM. Refer to the appropriate OEM service literature to determine the location.

Shop Talk

The ECM monitors the voltage level on this circuit. When the ECM commands the fan signal low, it expects the voltage level to be approximately 0 volts. If it detects a high voltage, this fault is recorded.

If Fault Code 2377 is still active after completing the following troubleshooting steps, 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:

  • Open circuit in the engine harness or fan control solenoid
  • Short circuit to voltage source in the OEM harness
  • Failed ECM.

Refer to Troubleshooting Fault Code t05-2377

Last Modified:  08-Jul-2010