Diagnostic Instructions
DTC Descriptor
DTC C0306: Motor A or B Circuit Malfunction
Circuit/System Description
The transfer case motor is a bi-directional, permanent magnet, DC 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 the following ranges:
This DTC detects an open, short to voltage or short to ground in the motor control A or motor control B circuits or an open or short to ground inside the motor.
Conditions for Running the DTC
| • | System voltage is 9-18 volts. |
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 control A or motor control B circuits when a high voltage is expected. |
| • | The fault must remain current for 30 seconds to set the DTC. |
Action Taken When the DTC Sets
| • | All shifting is disabled. |
| • | The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle. |
| • | The transfer case shift control module provides a reference voltage of 4.5 volts on the motor A/B line for diagnostic purposes. |
Conditions for Clearing the DTC
| • | The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present. |
| • | A history DTC clears after 100 consecutive ignition cycles without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Transfer Case Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
