NVG 136 Transfer Case

CIRCUIT DESCRIPTION
The transfer case encoder motor is a permanent magnet D.C. 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 a power supply relay (Motor A) circuit that supplies voltage to the motor through CKT 1552. The Motor B circuit (CKT 1553) 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 power on circuits 1552 and 1553.

CONDITIONS FOR SETTING THE DTC
1. The system will test the motor circuits by checking for unwanted voltage.
2. The system supplies voltage on the Motor A circuit and reads the voltage back on the Motor B circuit.
3. The transfer case shift control module senses a high voltage return on circuits 1552 or 1553 when a low voltage is expected.
4. If the system detects a problem with the circuits, the DTC is logged.

ACTION TAKEN WHEN THE DTC SETS
- All clutch activation (slip control) will be disabled.
- The SERVICE AWD/4WD lamp will be latched on for the remainder of the current ignition cycle.

CONDITIONS FOR CLEARING THE MIL/DTC
- Current Diagnostic Trouble Codes (DTC)
The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.
- History DTC
- Once 100 consecutive ignition cycles without a fault present.
- You issue a scan tool CLEAR CODES command.