PACCAR PX-9 CM2350 (2013-17) Fault Code:3634 PID: SPN:5484 FMI:4 Engine Fan Clutch 2 Control Circuit – Voltage Below Normal or Shorted to Low Source

Reason:
Engine Fan Clutch 2 Control Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the fan control circuit when commanded ON.

Effect:
The fan can 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 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 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 solenoid is an OEM device and the location is dependent upon the OEM. Refer to the OEM service manual for component 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 Engine Control Module (ECM) detected the fan control circuit pulse width modulated (PWM) signal was not at system voltage when the pulse width modulated (PWM) signal was commanded ON.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
1) To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults.

Shop Talk:
N/A

Possible Causes:
1) A short circuit to ground in the OEM harness
2) A malfunctioning fan clutch solenoid