CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 245

Fan Control Circuit – Voltage Below Normal or Shorted to Low Source


Fault Code: 245
PID: S033
SPN: 647
FMI: 4/4
LAMP: Amber

Fan Control Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the fan control circuit when commanded ON.

The fan can possibly stay on continuously or not run at all.

Fan Control Circuit

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 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. 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 the OEM. Certain OEMs may use a solenoid return that is wired to the ECM or can use a return that goes to engine block or chassis ground.

Component Location

The control solenoid location varies by OEM. Refer to the appropriate OEM troubleshooting and repair manual to determine the location.

Conditions for Running the Diagnostics

This 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 Codes

The fan control circuit PWM signal is not detected to be system voltage when the PWM signal is turned ON.

Action Taken When the Fault Code is Active

  • The 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 Code

The ECM will turn off the amber CHECK ENGINE light and the fault code state will become inactive immediately after the diagnostic runs and passes. The fault code can also be cleared by using the INSITE™ electronic service tool.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

The fan control logic can be adjusted with the 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 troubleshooting and repair manual for procedures to check the fan control circuit for a short circuit to ground.

Refer to Troubleshooting Fault Code t05-245

Last Modified:  16-Jul-2010