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Pinpoint Test Q: Four-Wheel Drive (4WD) Does Not Engage At Speed Correctly




Four Wheel Drive (4WD) Systems - 2-Speed Torque-On-Demand

Pinpoint Test Q: Four-Wheel Drive (4WD) Does Not Engage at Speed Correctly

Refer to Wiring Diagram Set 34, Four-Wheel Drive System for schematic and connector information Electrical Diagrams.

Normal Operation

When the operator selects a transfer case mode from 2H mode, the Transfer Case Control Module (TCCM) engages a clutch for approximately 5 seconds to synchronize the front and rear driveshafts allowing a mechanical engagement of the transfer case. The TCCM (Transfer Case Control Module) also removes the ground path from the Integrated Wheel End (IWE) solenoid, which removes vacuum from the IWEs (Integrated Wheel Ends), allowing them to engage the front axle shaft. Systematically check the necessary inputs and outputs at the TCCM (Transfer Case Control Module), internal components of the transfer case, IWE (Integrated Wheel End) components and drive axles.

- DTC P1825:00 (4-Wheel Drive Clutch Relay Open Circuit: No Sub Type Information)- Fault sets when TCCM (Transfer Case Control Module) C2371B pin 1 detects an open circuit. The TCCM (Transfer Case Control Module) disables transfer case synchronization clutch operation.

- DTC P1826:00 (4-Wheel Drive Low Clutch Relay Circuit To Battery: No Sub Type Information)- Fault sets when TCCM (Transfer Case Control Module) C2371B pin 1 detects a short to voltage. Transfer case synchronization clutch operation, though disabled by the TCCM (Transfer Case Control Module), is fully engaged when this DTC is present.

- DTC P1827:00 (4-Wheel Drive Low Clutch Relay Circuit To Ground)- Fault sets when TCCM (Transfer Case Control Module) C2371B pin 1 detects a short to ground. The TCCM (Transfer Case Control Module) disables transfer case synchronization clutch operation.

This pinpoint test is intended to diagnose the following:

- Transfer case synchronization clutch

- Transfer case

- TCCM (Transfer Case Control Module)

- Front axle assembly

- Wiring, terminals or connectors

PINPOINT TEST Q : 4WD (Four-Wheel Drive) DOES NOT ENGAGE AT SPEED CORRECTLY

Q1 RETRIEVE TCCM (Transfer Case Control Module) DTCs

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: Self-Test- TCCM (Transfer Case Control Module).

Are any DTCs retrieved?

Yes
For DTC P1825:00, GO to Q11.

For DTC P1826:00, GO to Q13.

For DTC P1827:00, GO to Q10.

For all other DTCs, GO to the Transfer Case Control Module (TCCM) DTC Chart. Four Wheel Drive (4WD) Systems - 2-Speed Torque-on-Demand

No
GO to Q2.

Q2 CHECK 4X4 MODE ENGAGEMENT AT REST

- Switch the Mode Select Switch (MSS) from 4X2 mode to 4X4 mode.

Does 4X4 mode engage at rest correctly?

Yes
GO to Q3.

No
GO to Pinpoint Test N. Pinpoint Test N: The Front Axle Does Not Engage/Disengage Correctly

Q3 CHECK 4X2 MODE TO 4X4 MODE SHIFT AT SPEED

- Switch the MSS (Mode Select Switch) to 4X2 mode.

- Drive the vehicle and carry out a 4X2 mode to 4X4 mode shift while driving at approximately 16 km/h (10 mph).

- Stop the vehicle, shift to 4X2 mode, drive the vehicle and carry out a 4X2 mode to 4X4 mode shift while driving at approximately 64 km/h (40 mph).

Does 4X4 mode engage correctly at 16 km/h (10 mph) and at 64 km/h (40 mph)?

Yes
GO to Pinpoint Test U. Pinpoint Test U: Four-Wheel Drive (4WD) System Functional Test

No
GO to Q4.

Q4 CHECK THE AVERAGE FRONT WHEEL SPEED (FRT_WHL_SPD) AND AVERAGE REAR WHEEL SPEED (REAR_WHL_SPD)

- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).

- Monitor the FRT_WHL_SPD and REAR_WHL_SPD PIDs while driving in a straight line.

Do the FRT_WHL_SPD and REAR_WHL_SPD PIDs match?

Yes
GO to Q5.

No
REFER to Antilock Brakes / Traction Control Systems to diagnose the wheel speed sensor concern.

Q5 CHECK THE TRANSFER CASE CLUTCH LOCKUP USING 4WD (Four-Wheel Drive) PWM (Pulse-Width Modulation) CLUTCH STATUS (4WD CLTCH_OUT) PID ACTIVE COMMAND

- With the vehicle in NEUTRAL, position it on a hoist.

- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).

- Switch the MSS (Mode Select Switch) to AUTO mode.

- Using the 4WD CLTCH_OUT active command, command the PID to 98%.

- Rotate the rear driveshaft while observing the front driveshaft.

Does the front driveshaft rotate when the rear driveshaft is rotated?

Yes
GO to Q6.

No
GO to Q9.

Q6 CHECK THE TRANSFER CASE CLUTCH RELEASE USING 4WD (Four-Wheel Drive) PWM (Pulse-Width Modulation) CLUTCH STATUS (4WD CLTCH_OUT) PID ACTIVE COMMAND

- With the vehicle still in NEUTRAL and on a hoist, using the 4WD_CLTCH_OUT active command, command the transfer case clutch to 0%.

- Rotate the rear driveshaft while observing the front driveshaft.

Does the front driveshaft rotate when the rear driveshaft is rotated?

Yes
GO to Q15.

No
End the active command. GO to Q7.

Q7 CHECK THE TRANSFER CASE ENGAGEMENT (ON A HOIST)

- Start the engine, switch the MSS (Mode Select Switch) to 4X2 mode.

- Place the transmission in DRIVE and increase speed to between 16 km/h (10 mph) and 24 km/h (15 mph).

- While observing the front driveshaft, switch the MSS (Mode Select Switch) to 4X4 mode.

Did the front driveshaft start to spin?

Yes
GO to Q8.

No
GO to Q15.

Q8 CHECK THE TRANSFER CASE DISENGAGEMENT

- Switch the MSS (Mode Select Switch) to 4X2 mode while observing the front driveshaft.

Does the front driveshaft rotate?

Yes
GO to Q15.

No
GO to Pinpoint Test N. Pinpoint Test N: The Front Axle Does Not Engage/Disengage Correctly

Q9 CHECK CLUTCH CONTROL CIRCUIT FOR VOLTAGE USING THE 4WD (Four-Wheel Drive) PWM (Pulse-Width Modulation) CLUTCH STATUS (4WD_CLTCH_OUT) ACTIVE COMMAND

- Using the 4WD_CLTCH_OUT active command, command the transfer case clutch to 98%.

- Measure the voltage by carefully back-probing transfer case C350-16, circuit CCF03 (GY/BN), component side and the transfer case housing.





Is the voltage greater than 9 volts?

Yes
END the active command. INSTALL a new transfer case synchronization clutch. CLEAR the DTCs. TEST the system for normal operation.

No
GO to Q10.

Q10 CHECK THE TRANSFER CASE-TO-CHASSIS GROUND USING THE 4WD (Four-Wheel Drive) PWM (Pulse-Width Modulation) CLUTCH STATUS (4WD_CLTCH_OUT) ACTIVE COMMAND

- Using the 4WD_CLTCH_OUT active command, command the transfer case clutch to 98%.

- Measure the voltage by carefully back-probing transfer case C350-16, circuit CCF03 (GY/BN), component side and chassis ground.





Is the voltage greater than 9 volts?

Yes
END the active command. REPAIR the transfer case ground connection between the transfer case and the chassis. CLEAR the DTCs. TEST the system for normal operation.

No
GO to Q11.

Q11 CHECK CLUTCH CONTROL CIRCUIT FOR A SHORT TO GROUND

- Ignition OFF.

- Disconnect: Transfer Case C350.

- Disconnect: TCCM (Transfer Case Control Module) C2371B.

- Measure the resistance between transfer case C350-16, circuit CCF03 (GY/BN), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to Q12.

No
REPAIR circuit CCF03 (GY/BN). CLEAR the DTCs. TEST the system for normal operation.

Q12 CHECK CLUTCH CONTROL CIRCUIT FOR AN OPEN

- Ignition OFF.

- Disconnect: Transfer Case C350 (if not previously disconnected).

- Disconnect: TCCM (Transfer Case Control Module) C2371B (if not previously disconnected).

- Measure the resistance between transfer case C350-16, circuit CCF03 (GY/BN), harness side and TCCM (Transfer Case Control Module) C2371B-1, circuit CCF03 (GY/BN), harness side.





Is the resistance less than 3 ohms?

Yes
GO to Q13.

No
REPAIR circuit CCF03 (GY/BN). CLEAR the DTCs. TEST the system for normal operation.

Q13 CHECK CLUTCH CONTROL CIRCUIT FOR VOLTAGE USING THE 4WD (Four-Wheel Drive) PWM (Pulse-Width Modulation) CLUTCH STATUS (4WD_CLTCH_OUT) PID ACTIVE COMMAND

- Connect: Transfer Case C350.

- Connect: TCCM (Transfer Case Control Module) C2371B.

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).

- Using the 4WD_CLTCH_OUT active command, command the transfer case clutch to greater than 10%.

- Measure the voltage by carefully back-probing transfer case C350-16, circuit CCF03 (GY/BN), component side and ground.





Is any voltage present?

Yes
END the active command. GO to Q14.

No
END the active command. INSTALL a new transfer case synchronization clutch. CLEAR the DTCs. TEST the system for normal operation.

Q14 CHECK CLUTCH CONTROL CIRCUIT FOR A SHORT TO VOLTAGE USING THE 4WD (Four-Wheel Drive) PWM (Pulse-Width Modulation) CLUTCH STATUS (4WD_CLTCH_OUT) ACTIVE COMMAND

- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).

- Using the 4WD_CLTCH_OUT active command, command the transfer case clutch to 0%.

- Measure the voltage by carefully back-probing transfer case C350-16, circuit CCF03 (GY/BN), component side and ground.





Is any voltage present?

Yes
REPAIR circuit CCF03 (GY/BN). CLEAR the DTCs. TEST the system for normal operation.

No
GO to Q15.

Q15 CHECK FOR CORRECT TCCM (Transfer Case Control Module) OPERATION

- Ignition OFF.

- Disconnect all TCCM (Transfer Case Control Module) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect all TCCM (Transfer Case Control Module) connectors and make sure they are seated correctly.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new TCCM (Transfer Case Control Module). REFER to 4X4 Control Module . CLEAR the DTCs. TEST the system for normal operation.

No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. ADDRESS the root cause of connector or pin issue.

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