NVG 126-NP4 Transfer Case

DTC C0306





Circuit Description
The transfer case encoder motor is a permanent magnet, D.C. motor and gear reduction assembly. When energized through motor feed A, motor control B provides the ground through the transfer case shift control module ground circuit. The motor, through a series of gears, rotates the sector shaft of the transfer case which applies varying force to a set of clutch plates controlling the torque applied to the front wheels.
This DTC detects an open, short to voltage, or short to ground in the motor feed A or motor control B circuits, an open in the module ground circuit, or an open, or short to ground inside the motor.

Conditions for Setting the DTC
^ The system tests the motor circuits by checking for unwanted voltage.
^ Then, the system supplies voltage on each of the motor circuits and reads the voltage back on the other circuit.
^ If the system detects a condition with the circuits, the DTC is logged. The transfer case shift control module senses a low voltage return in the motor feed A or motor control B circuits when a high voltage is expected.
^ The fault must remain current for 30 seconds to set the DTC.
^ The transfer case shift control module provides a reference voltage of 4.5 volts on the motor A/B line for diagnostic purposes.

Action Taken When the DTC Sets
^ All shifting is disabled.
^ The SERVICE AWD indicator is latched on for the remainder of the current ignition cycle.

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.
2. This step tests the encoder motor for an internal short to ground.
3. This step helps isolate motor malfunctions from the transfer case shift control module and wiring.
4. This step tests for an open, high resistance, short to ground, or short to voltage.