Circuit Description
The transfer case encoder motor has a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, 2HI, and 4L ranges.
This DTC detects a short or open in the battery positive voltage circuit (CKT 1640), ground circuit, an internal short in the motor windings and related circuitry, or an internal transfer case shift control module failure.
Action Taken When the DTC Sets
In the event that one of the motor control circuits is energized (battery voltage is applied) the transfer case shift control module will energize the other motor control circuit to keep the motor from running. All switch indicator lamps will flash continuously to prompt the driver that service is required. The transfer case system will be disabled and the transfer case shift control module will remain energized even with the ignition in the OFF position.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present and a momentary loss of battery power at the battery positive voltage circuit (CKT 40).
Diagnostic Aids
When the vehicle is equipped with a manual transmission the clutch pedal must be depressed and working correctly in order for the transfer case to shift to the 4 low position. In order to confirm that it is operating correctly go the engine data 1 screen under the engine data display and observe the clutch pedal switch parameter.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the battery positive voltage circuit (CKT 1640) for an open or high resistance.
-
This step inspects the ATC fuse for an open.
-
This step tests the ground circuit.
-
This step tests the Motor Control A and B circuits.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Check the transfer case shift control module for DTCs. The transfer case shift control module is not a class 2 device. DTCs are displayed on the transfer case shift control switch. Use the following four steps to obtain
DTCs.
Did you perform A Diagnostic System Check - Transfer Case? | -- | Go to Step 2 | Go to Diagnostic System Check |
Does the voltage measure near the specified value? | B+ | Go to Step 6 | Go to Step 3 | |
Inspect the ATC Fuse 20A. Is the fuse blown? | -- | Go to Step 5 | Go to Step 4 | |
4 | Repair the battery positive voltage circuit (CKT 1640) for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- |
5 | Repair the battery positive voltage circuit (CKT 1640) for a short to voltage or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Replace the ATC Fuse. Did you complete the repair? | -- | Go to Step 11 | -- |
Connect a test lamp from the battery positive voltage circuit (CKT 1640) to the ground circuit at the transfer case shift control module. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 7 | |
7 | Repair the ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- |
Does the voltage measure near the specified value? | +12V/-12V | Go to Step 9 | Go to Step 10 | |
9 | Repair the open or high resistance in the transfer case motor control A or B circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. If OK, replace the transfer case encoder motor. Refer to Motor/Encoder Replacement . Did you complete the repair? | -- | Go to Step 11 | -- |
10 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
