Circuit Description
The transfer case motor is 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 the following ranges:
| • | 2HI |
| • | 4HI |
| • | 4LO |
| • | Neutral |
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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0306 Motor A or B Circuit Malfunction
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The 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 will clear the DTC if the condition for setting the DTC is not currently present. |
| • | 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.
-
This step tests the battery positive and ground circuits for poor connections.
-
This step tests the encoder motor for an internal short to ground.
-
This step helps isolate motor malfunctions from the transfer case shift control module and wiring.
-
This step test for an open, high resistance, short to ground or short to voltage.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Check the battery positive and ground circuits for poor connections. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 3 | |
|
Important: Use test leads designed for this connector and make firm contact with the leads.
Is motor control A or motor control B shorted to ground? | -- | Go to Step 6 | Go to Step 4 | |
Important: Use test leads designed for this connector and make firm contact with the leads. Is the motor/encoder within the specified values? | 0.3-35 ohms | Go to Step 5 | Go to Step 6 | |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 | |
6 | Replace the encoder motor. Refer to Transfer Case Encoder Motor Replacement . Did you complete the repair? | -- | Go to Step 8 | -- |
7 | Replace the transfer case shift control module. Refer to Control Module References for replacement, set-up, and programming. Did you complete the repair? | -- | Go to Step 8 | -- |
8 |
Does the DTC set? | -- | Go to Step 2 | System OK |
