NVG 136 Transfer Case

CIRCUIT DESCRIPTION
The transfer case shift control module uses the VIN information for calculations that are required for the different calibrations used based on axle ratio, transmission, tire size, and engine. The system does not know which calibration to use without this information.

CONDITIONS FOR SETTING THE DTC
The transfer case shift control module does not receive a valid VIN digit for the correct application, K truck, L van or T truck within 3 seconds after power up.

ACTION TAKEN WHEN THE DTC SETS
- The ignition counts since last fault will be cleared.
- The system will be disabled until valid VIN data is received.
- The SERVICE AWD/4WD lamp will be latched on.

CONDITIONS FOR CLEARING THE MIL/DTC
A history Diagnostic Trouble Code (DTC) will clear after a valid VIN digit is received.

POSSIBLE CAUSES
Class 2 Data bus malfunction, Vehicle Control Module (VCM) malfunction, module installed in wrong vehicle.

DIAGNOSTIC AIDS
1. Using a Scan Tool, check all components connected to the Class 2 serial data line.
2. Check the Vehicle Control Module (VCM) calibration for a miscalculated EEPROM
3. Check the transfer case shift control module part number for an incorrect part number