C0387
DTC C0387Circuit Description
The transfer case encoder is a switch that converts a shaft position, representing a mode or range position, into electrical signals for use by the transfer case shift control module. The encoder houses 4 Hall effect sensors that are used for channels P, A, B, and C. These sensors provide a path to ground, when a magnet, (part of the Motor Encoder), passes over them.
The transfer case shift control module supplies an 8 V reference and a ground circuit for the encoder Hall effects sensors to function.
The transfer case shift control module supplies current limited 5 V on all the channels, thus as these channels are pulled to ground, the module can interpret the location of the transfer case shift position.
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 circuit 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 4LO or 4HI.
Action Taken When the DTC Sets
^ The SERVICE 4WD indicator 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 numbers below refer to the step numbers on the diagnostic table.
3. Tests whether the transfer case shift control module is sensing any change in all of the encoder channels.
4. Helps determine whether the shift is prevented due to a mechanical fault.
5. Tests whether the transfer case shift control module is sensing any change in any of the encoder channels.
6. Tests if proper reference voltage is being supplied to the encoder from the suspect circuit.
7. Helps determine whether a short between 2 or more encoder circuits exist.
8. Helps determine whether the shift is prevented due to a mechanical fault.
9. Tests for the electrical energizing of the encoder motor.
10. Tests the suspect circuit(s) for an open or a short to power.
11. Tests for short between the suspect circuits.