Circuit Description
The transfer case encoder motor is a permanent magnet DC motor and gear reduction assembly. The encoder motor is controlled with a pulse width modulated (PWM) circuit within the transfer case shift control module. This circuit consists of Motor Control A, a power supply relay circuit that supplies voltage to the motor. The Motor Control B circuit is a PWM driver that varies the duty cycle to control the amount of current through the motor to ground.
This DTC detects a short to ground on the Motor Control A circuit or the Motor Control B circuit.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0308 Motor A/B Circuit Low
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The system voltage is 9-16 volts. |
Conditions for Setting the DTC
| • | The system tests the motor circuits by testing for unwanted voltage. |
| • | The system supplies voltage on the Motor Control A circuit and reads the voltage back on the Motor Control B circuit. |
| • | The transfer case shift control module senses a low voltage return on the Motor Control A circuit or the Motor Control B circuit when a high voltage is expected. |
| • | If the system detects a condition with the circuits, the DTC is logged. |
Action Taken When the DTC Sets
| • | The SERVICE AWD indicator remains illuminated for the remainder of the current ignition cycle. |
| • | All clutch activation, or slip control is disabled. |
Conditions for Clearing the DTC
Current DTC
The transfer case shift control module clears the DTC if the condition for setting the DTC no longer exists.
History DTC
| • | A history DTC clears 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.
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This step tests Motor Control A for an open or short to ground.
-
This step tests Motor Control B for an open or short to ground.
-
This step tests for continuity across the motor windings.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
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Important: The transfer case Motor Control circuits have capacitors connected between their circuit and ground. As the capacitor charges it can give the indication of a short circuit. When making resistance checks with a DMM, allow the reading to stabilize for at least 10 seconds before making the final measurement.
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 3 | |
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Important: The transfer case Motor Control circuits have capacitors connected between their circuit and ground. As the capacitor charges it can give the indication of a short circuit. When making resistance checks with a DMM, allow the reading to stabilize for at least 10 seconds before making the final measurement. Test Motor Control B for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 4 | |
With a DMM measure the resistance across the motor windings. Were the resistance values within the specified range? | 0.5-35 ohms | Go to Step 5 | Go to Step 6 | |
5 | Test the motor windings for a short to ground by checking resistance from motor control A and motor control B to ground. Refer to Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 7 |
6 | Replace the encoder motor. Refer to Transfer Case Motor/Encoder Replacement . Is the repair complete? | -- | Go to Step 8 | -- |
7 | Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Is the repair complete? | -- | Go to Step 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
