C0374
DTC C0374
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC C0374 54
- General System Performance Temperature High
Diagnostic Fault Information
Circuit/System Description
The general system performance DTC sets based on a thermal module within the transfer case shift control module (TCCM) software. The components included in this thermal model are the motor driver within the TCCM, the transfer case shift motor, and the clutch inside the transfer case.
This fault occurs when one of the three components included in the thermal model surpass the upper limits of this model indicating possible damage to the transfer case or other driveline components. This DTC detects an over temperature condition base on a thermal model.
Conditions for Running the DTC
* Ignition ON.
* System voltage 10.5-18 V.
* DTC C0379 is not set.
* Vehicle speed > 5 kph (3 mph)
Conditions for Setting the DTC
This DTC sets if one of three components: motor driver inside the TCCM, transfer case clutch, or the shift motor, exceed the thermal model within the software for the module.
Action Taken When the DTC Sets
* All range and mode changes disabled until thermal model indicates temperature acceptable.
* The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.
Conditions for Clearing the DTC
* The TCCM clears the DTC once the conditions for setting the DTC are no longer present.
* A history DTC clears after 40 consecutive warm-up cycles without a fault present.
* History and current DTCs can be cleared using a scan tool.
Diagnostic Aids
* The TCCM provides a reference voltage of 1.25-3.75 V on the motor B circuit for diagnostic purposes.
* It is possible to have windings inside the motor short to the case resulting in a short to ground.
* A problem where the front axle actuator is unable to mechanically engage can cause this DTC to set.
* A worn transfer case clutch can cause this DTC to set.
* A motor brake not holding can cause this DTC to set.
* Faulty wheel speed sensors can cause this DTC to set. When driving at a steady speed, the scan tool should display the same values for the following data parameters in the electronic brake control module (EBCM):
- Left and right front wheel speed sensors
- Left and right rear wheel speed sensors
Reference Information
Schematic Reference
Transfer Case Control Schematics (MP 3023/3024-NQH - Transfer Case)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Transfer Case Description and Operation (Transfer Case Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information.
Circuit/System Verification
1. Ignition ON, engine OFF.
2. Install a scan tool.
3. Ensure no other ECBM or TCCM codes are set.
• If any other EBCM or TCCM DTC's are set, diagnose them first.
Circuit/System Testing
1. Engage parking brake.
2. Block rear wheels.
3. Lift front wheels.
4. Key ON, engine OFF. Install scan tool.
5. Transfer case in 2WD HI. Transmission in Neutral.
6. Mechanical binding. - Using the Special Functions capability of the scan tool, engage the front axle. While holding one front tire stationary, spin the other tire. The front propshaft should turn.
• If the front propshaft does not turn, inspect the front axle clutch fork for mechanical binding.
7. Wheel speed sensors. - Take the vehicle on a short test drive on a smooth and level road. Using the Data Display function of the ECBM feature of the scan tool, verify that the front and rear wheel speeds sensors display do not vary or become intermittent.
• If while driving at a steady speed the RPM values vary or becomes intermittent, check the EBCM for wheel speed DTC's. Wheel speed DTC's diagnostics are in antilock brake systems.
8. Transfer case encoder motor brake. - Using a scan tool, clear DTC's. Shift the vehicle to 2WD HI. Monitor the transfer case motor amperage parameter in the Data Display feature of the scan tool. Using the transfer case shift control switch, command the transfer case to the 4WD HI mode. The transfer case motor amperage should increase while the motor is shifting and then return to 0 amps within 5 seconds or less.
• If the amperage stays high longer than 5 seconds, this indicates the brake is not holding. Replace the transfer case motor.
9. Transfer case clutch integrity. - Shift the vehicle into 4WD HI and take it for a test drive. Clear the DTC if possible. Monitor front and rear wheel speeds using the EBCM data display. Under heavy acceleration the front and rear wheel speeds should be similar.
• If the front wheel speeds are much lower, this indicates a weak clutch and a transfer case tear down and inspection will be required.
10. If all prior evaluations test normal, reprogram the TCCM and perform the ATC Motor Learn procedure in the Special Functions feature of the scan tool or the Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset) procedure in the service manual.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control Module References (Control Module References) for TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset) for Motor Learn Procedure
* Four-Wheel Drive Does Not Engage (Four-Wheel Drive Does Not Engage)
* Front Drive Axle Clutch Fork Inspection (Front Drive Axle Clutch Fork Inspection)
* Transfer Case Assembly Replacement (Transfer Case Assembly Replacement)