Pinpoint Test T: The Vehicle Does Not Shift Between 4H and 4L Modes Correctly

Four Wheel Drive (4WD) Systems - Electronic Shift

Pinpoint Tests

Pinpoint Test T: The Vehicle Does Not Shift Between 4H and 4L Modes Correctly

Refer to Wiring Diagram Set 34, Four-Wheel Drive Systems for schematic and connector information. Diagrams By Number

Normal Operation

The high-low shift occurs when the reduction shift fork moves the high-low collar to lock the planetary gear set to the output shaft. The torque transmitted through the sun gear from the input shaft turns the front planetary gear set assembly. The front planetary gear set assembly, now engaged, provides transfer case speed reduction. Certain criteria, such as vehicle speed and Transmission Range (TR) selection must be met before this shift can occur. Systematically check the necessary inputs and outputs of the Transfer Case Control Module (TCCM), components of the transfer case, Integrated Wheel End (IWE) components and halfshafts.

- DTC C1729:00 (Transfer Case Unable to Transition Between 4H and 4L) - Fault sets when target shift motor position is not reached after the maximum number of allowed blocked shift retries for 4H to 4L or 4L to 4H. Requested shift motor position is not reached.

This pinpoint test is intended to diagnose the following:
- Transmission neutral switch
- Transmission drag torque
- ABS wheel speed inputs
- High Speed Controller Area Network (HS-CAN)

PINPOINT TEST T: THE VEHICLE DOES NOT SHIFT BETWEEN 4H AND 4L MODES 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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T1 CHECK FOR DTCs

- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self Test - TCCM.
- Are any DTCs present?

Yes
For DTC C1729:00, GO to T2.

For all other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Four Wheel Drive (4WD) Systems - Electronic Shift

No
GO to Pinpoint Test S. Pinpoint Test S: The Vehicle Does Not Shift Between 2H and 4H Correctly and/or Grinding Noise Heard During Four-Wheel Drive (4W

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T2 CHECK THE 2H TO 4H SHIFT

- Drive the vehicle and shift from 2H to 4H.
- Does the vehicle shift between 2H and 4H correctly?

Yes
GO to T3.

No
GO to Pinpoint Test S. Pinpoint Test S: The Vehicle Does Not Shift Between 2H and 4H Correctly and/or Grinding Noise Heard During Four-Wheel Drive (4W

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T3 CHECK THE 4H TO 4L SHIFT

- NOTE: When shifting in or out of 4L, the transmission must be in NEUTRAL and the vehicle stopped or moving less than 5 km/h (3 mph).

- Drive the vehicle and shift Mode Select Switch (MSS) from 4H to 4L.
- Does the transfer case shift from 4H to 4L correctly and the complaint is related to a clunk noise during the shift?

Yes
Transmission neutral drag is excessive. REFER to Automatic Transaxle/Transmission - 6R80 Testing and Inspection for transmission diagnosis.

No
GO to T4.

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T4 CHECK THE NEUTRAL INDICATOR (NEUTRAL) AND ABS MODULE WHEEL SPEED PIDs

- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- A. Monitor the NEUTRAL PID while shifting the transmission through gear ranges.
- Enter the following diagnostic mode on the scan tool: DataLogger - ABS Module.
- B. Monitor the wheel speed PIDs:

- Left Front Wheel Speed Sensor (LF_WSPD)
- Left Rear Wheel Speed Sensor (LR_WSPD)
- Right Front Wheel Speed Sensor (RF_WSPD)
- Right Rear Wheel Speed Sensor (RR_WSPD)
- A. Does the NEUTRAL PID indicate True when the transmission is shifted to NEUTRAL?

B. Do the wheel speed PIDs indicate 0 km/h (0 mph)?

Yes
If all 5 PIDs are accurate, GO to Pinpoint Test S. Pinpoint Test S: The Vehicle Does Not Shift Between 2H and 4H Correctly and/or Grinding Noise Heard During Four-Wheel Drive (4W

No
A. REFER to Automatic Transaxle/Transmission - 6R80 Testing and Inspection (4R75E transmission) or Automatic Transaxle/Transmission - 6R80 Testing and Inspection (6R80 transmission) for further diagnosis of the TR sensor and the HS-CAN communication network.

B. REFER to Vehicle Dynamic Systems Testing and Inspection for further diagnosis of the ABS system and the HS-CAN communication network.

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