Diagnostic Instructions
DTC Descriptor
DTC C0321: Transfer Case Lock Circuit Malfunction
Circuit/System Description
The transfer case shift control module controls the transfer case lock solenoid. The transfer case lock solenoid is released by being energized. This is accomplished by grounding the lock solenoid control circuit during gears shifts and in the AUTO or
adapt mode. Locking action is applied when power or ground is taken away from the lock solenoid. The transfer case motor is prevented from moving. The system is capable of providing a 2HI, 4HI and 4LO lock-up without the need of additional vehicle power
to hold the transfer case in these positions.
This DTC detects an open lock solenoid coil, open motor lock control circuit or an open motor lock feed circuit.
Conditions for Running the DTC
| • | System voltage is 9-18 volts. |
Conditions for Setting the DTC
| • | The transfer case shift control module tries to unapply, turn OFF, the lock solenoid by grounding the motor control circuit. |
| • | If the module does not sense the battery voltage at the motor lock control circuit prior to applying the motor lock, the DTC will set. |
| • | Transfer case lock output reads back as a high voltage when a low voltage is expected. |
Action Taken When the DTC Sets
| • | All shifting is disabled. |
| • | The SERVICE 4WD indicator remains illuminated 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 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.
