C0388
DTC C0388
Circuit Description
The rear differential control circuit consists of an actuator which engages and disengages the rear axle differential lock. The rear differential actuator consists of a coil assembly, and a locking assembly with springs and pins to lock the rear differential, all within the rear differential assembly.
The rear axle differential lock actuator consists of the following circuits:
* The rear differential lock control circuit, which is connected to the transfer case shift control module and supplies battery voltage.
* The rear differential lock return ground circuit, which is also connected to the transfer case shift control module.
Whenever the rear differential lock has been requested the transfer case shift control module provides battery voltage through the rear differential lock control circuit, and provides ground through the rear differential lock return circuit through a current limiting driver.
Whenever a rear differential lock is requested the transfer case must be in 4 LO and the vehicle speed must be below 5 km/h (3 mph) for the request to be accepted. The rear differential lock will remain locked up to 32 km/h (20 mph) after which the rear differential lock will disengage.
This DTC detects a short to ground, short-to-voltage, or an open circuit.
Conditions for Running the DTC
* The ignition is ON.
* The system voltage is 9-18 volts.
Conditions for Setting the DTC
* The transfer case shift control module monitors the state of the rear axle differential lock actuator. The transfer case shift control module reads the rear differential lock control, and the rear differential lock return circuits for a high and low voltage. The DTC will set if these circuits are high when a low voltage is expected or when the circuits are low when a high voltage is expected.
* The DTC will set if this circuit is high when a low voltage is present or when the circuit is low when a high voltage is present.
Action Taken When the DTC Sets
* All rear differential lock requests will be disabled. Transfer case mode shifts will not be affected.
* SERVICE 4WD indicator will be 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 is not currently present.
* A history DTC will clear after 33 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 determines of the coil has excessive resistance or if the windings are shorted together.
3. This step determines if the coil or pigtail is shorted to ground.
4. This step determines if either the differential lock control or differential lock return circuits are shorted to ground.
5. This step determines if the differential lock control and differential lock return circuits are shorted together.
6. This step tests for an open or high resistance in both the return and control circuits.
7. This step refers to transfer case shift control module replacement.
8. This step refers to encoder motor replacement.
