C0387

Circuit Description
The transfer case encoder motor is a bi-directional, permanent magnet, DC motor. The motor, through a series of gears, rotates a sector shaft which moves the mode and range forks to shift the transfer case between 4H, AUTO (Adapt), 2H, N, and 4L ranges. The transfer case encoder motor is used to perform the requested shift, the motor lock holds the clutch pack in place, and the encoder is used to provide feedback.
This DTC detects that the transfer case is unable to successfully complete a shift to a requested mode or range.
Conditions for Setting the DTC
^ The transfer case shift control module will test the motor circuits and determine that there are no motor faults existing.
^ The transfer case shift control module has attempted to shift to a requested mode/range and has failed to reach the desired position.
^ The transfer case shift control module has performed a default shift to 41_0 or 4HI.
Action Taken When the DTC Sets
^ The SERVICE indicator (AWDAWD) lamp will be latched on for the remainder of the current ignition cycle.
^ All shifting will be disabled.
^ The range/mode lights will be disabled
^ The next ignition cycle, the transfer case shift control module will power-up as if the 4HI was the mode present when the ATC was powered down.
Conditions for Clearing the DTC
^ The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ History DTCs can be cleared using a scan tool.








Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step check to see if the encoder motor moves.
3. This step determines if the transfer case sector shaft is bound up.
5. This step tests the continuity of the effected encoder circuits.
6. This step tests the effected encoder circuits for a short to ground.
7. This step tests the effected encoder circuits for a short to voltage.
8. This step determines if the transfer case sector shaft is bound up.