SPN 647 - FMI 3 (Fault Code 2377)
SPN647 FMI3
Fan Control Circuit - Voltage Above Normal or Shorted to High Source
 |
| ISB, ISC, and ISL - Fan Control Circuit |
Fault Code: 2377
PID(P), SID(S): S033
SPN: 647
FMI: 3/3
Lamp: Amber
REASON: Fan Control Circuit - Voltage Above Normal or Shorted to High Source. Open circuit or high voltage detected at the fan control circuit.
EFFECT: The fan may stay on continuously or not run at all.
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. 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 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 appropriate OEM service literature to determine the location.
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:
For ON/OFF and variable speed fan, the diagnostic will clear when the fan is turned off and the diagnostic runs and passes. For all other fan types, the diagnostic will clear when the fan PWM signal is less than 100 percent.
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.
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-VDC. 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 troubleshooting and repair manual 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.
Read More:
Blog.Teknisi
0 Response to "SPN 647 - FMI 3 (Fault Code 2377)"
Post a Comment