Pinpoint Test H: The Four-Wheel Drive (4WD) Does Not Engage At Speed Correctly
Four Wheel Drive (4WD) Systems - Mechanical Shift
Pinpoint Tests
Pinpoint Test H: The Four-Wheel Drive (4WD) Does Not Engage at Speed Correctly
Refer to Wiring Diagram Set 34, Four-Wheel Drive Systems for schematic and connector information. Diagrams By Number
Normal Operation
When the operator selects 4H mode, the Transfer Case Control Module (TCCM) engages the synchronization clutch for approximately 5 seconds to synchronize the front and rear driveshafts allowing a further mechanical engagement of the transfer case. The TCCM also removes the ground path from the Integrated Wheel End (IWE) solenoid, which removes vacuum from the IWEs, allowing them to engage. Systematically check the necessary inputs and outputs at the TCCM, internal components of the transfer case and shift lever, IWE components and drive axles.
- DTC P1825:00 (4-Wheel Drive Clutch Relay Open Circuit: No Sub Type Information) - Fault sets when TCCM C2371B pin 1 detects an open circuit. The TCCM 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 C2371B pin 1 detects a short to voltage.
Transfer case synchronization clutch operation, though disabled by the TCCM, is fully engaged when this DTC is present.
- DTC P1827:00 (4-Wheel Drive Low Clutch Relay Circuit To Ground: No Sub Type Information) - Fault sets when TCCM C2371B pin 1 detects a short to ground. The TCCM disables transfer case synchronization clutch operation.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Transfer case synchronization clutch
- Transfer case internal components
- TCCM
PINPOINT TEST H: THE 4WD HIGH DOES NOT ENGAGE AT SPEED CORRECTLY
WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.
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H1 RETRIEVE DTCs
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self Test - TCCM.
- Are any DTCs present?
Yes
For DTC P1825:00, GO to H6.
For DTC P1826:00, GO to H11.
For DTC P1827:00, GO to H8.
For all other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Transfer Case Control Module (TCCM) DTC Chart
No
GO to H2.
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H2 CHECK THE 4H ENGAGEMENT AT REST
- With the vehicle at rest, shift to 4H.
- Confirm 4H engagement by driving the vehicle and check for wind-up in turns.
- Does 4H engage at rest correctly?
Yes
GO to H3.
No
GO to Pinpoint Test C. Pinpoint Test C: The Vehicle Does Not Shift Between 2H (4X2) And 4H (4X4 High) Correctly
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H3 CHECK THE TRANSFER CASE ENGAGEMENT AT SPEED
- Shift the transfer case to 2H.
- Drive the vehicle and carry out a 2H to 4H shift while driving at approximately 16 km/h (10 mph).
- Stop the vehicle, shift to 2H, drive the vehicle and carry out a 2H to 4H shift while driving at approximately 64 km/h (40 mph).
- Does the 4H engage correctly (or much better) at 16 km/h (10 mph) than at 64 km/h (40 mph)?
Yes
GO to H4.
No
GO to Pinpoint Test E. Pinpoint Test E: The Front Axle Does Not Engage/Disengage Correctly
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H4 CHECK THE TRANSFER CASE SYNCHRONIZATION CLUTCH LOCK-UP USING 4WD PWM CLUTCH STATUS (4WD_CLTCH_OUT) PID
- With the vehicle in NEUTRAL, position it on a hoist. Refer to Vehicle Jacking and Lifting.
- While in the vehicle, shift the transfer case to 4H mode.
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Command the PID 4WD_CLTCH_OUT to 98%.
- Shift the transfer case to 2H.
- Rotate the rear driveshaft while observing the front driveshaft.
- Does the front driveshaft rotate when the rear driveshaft is rotated?
Yes
GO to H5.
No
GO to H6.
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H5 CHECK THE TRANSFER CASE SYNCHRONIZATION CLUTCH RELEASE USING THE 4WD_CLTCH_OUT PID
- Command the PID 4WD_CLTCH_OUT 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 H10.
No
END the active command. GO to H6.
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H6 CHECK VOLTAGE TO THE TRANSFER CASE SYNCHRONIZATION CLUTCH USING THE 4WD_CLUTCH_OUT PID
- Ignition OFF.
- Disconnect: Transfer Case C3146.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM (if not done previously).
- While commanding the PID 4WD_CLTCH_OUT at 98%, measure the voltage between transfer case C3146-2, circuit CCF03 (GY/BN), harness side and the transfer case housing.
- Is the voltage greater than 10 volts?
Yes
END the active command. INSTALL a new transfer case synchronization clutch. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
No
GO to H7.
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H7 CHECK VOLTAGE TO THE TRANSFER CASE SYNCHRONIZATION CLUTCH USING THE 4WD_CLTCH_OUT PID
- While still commanding the PID 4WD_CLTCH_OUT at 98%, measure the voltage between transfer case C3146-2, circuit CCF03 (GY/BN), harness side and chassis ground.
- Is the voltage greater than 10 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. REPEAT the self-test.
No
END the active command. GO to H8.
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H8 CHECK THE TRANSFER CASE SYNCHRONIZATION CLUTCH CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: TCCM C2371B.
- Measure the resistance between transfer case C3146-2, circuit CCF03 (GY/BN) and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to H9.
No
REPAIR circuit CCF03 (GY/BN). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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H9 CHECK THE TRANSFER CASE SYNCHRONIZATION CLUTCH CIRCUIT FOR AN OPEN
- Disconnect: TCCM C3146 (if not done previously).
- Measure the resistance between transfer case C3146-2, circuit CCF03 (GY/BN), harness side and the TCCM C2371B-1, circuit CCF03 (GY/BN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to H12.
No
REPAIR circuit CCF03 (GY/BN). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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H10 CHECK FOR CORRECT TRANSFER CASE SYNCHRONIZATION CLUTCH RELEASE USING THE 4WD_CLTCH_OUT PID
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
- Ignition OFF.
- Disconnect: Transfer Case C3146.
- Ignition ON.
- While commanding 4WD_CLTCH_OUT at 98%, connect the 12-volt incandescent test light between transfer case C3146-2, circuit CCF03 (GY/BN), harness side and ground.
- Does the test light illuminate?
Yes
END the active command. GO to H11.
No
END the active command. CHECK the transfer case for a mechanical fault condition. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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H11 CHECK THE TRANSFER CASE SYNCHRONIZATION CLUTCH CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: TCCM C3146 (if not done previously).
- Disconnect: TCCM C2371B.
- Ignition ON.
- Measure the voltage between transfer case C3146-2, circuit CCF03 (GY/BN), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit CCF03 (GY/BN). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
No
GO to H12.
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H12 CHECK TRANSFER CASE SYNCHRONIZATION CLUTCH
- Ignition OFF.
- Measure the resistance between transfer case C3146 pin 1, component side and the transfer case housing.
- Is the resistance between 1-3 ohms?
Yes
GO to H13.
No
INSTALL a new transfer case synchronization clutch. REFER to Transfer Case Disassembly and Assembly. CLEAR the DTCs. TEST the system for normal operation.
REPEAT the self-test.
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H13 CHECK FOR CORRECT TCCM OPERATION
- Disconnect all TCCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all TCCM connectors and make sure they are seated correctly.
- Operate the system and verify the concern is still present, carry out the Mechanical Shift-On-The-Fly (MSOF) Functional Test. GO to Pinpoint Test J. Pinpoint Test J: Mechanical Shift-On-The-Fly (MSOF) Functional Test
- Is the concern still present?
Yes
INSTALL a new TCCM. REFER to Transfer Case Control Module (TCCM) Service and Repair. TEST the system for normal operation.
REPEAT the self-test.
No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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