NVG 236/246-NP8 (Two Speed Automatic)

Circuit Description
At each power up the module runs a self test on the following:
^ EEPROM checksum
^ ROM checksum
^ RAM checksum
^ RAM malfunction
Conditions for Setting the DTC
^ Critical operational parameters stored in EEPROM have failed checksum test indicating invalid data.
^ Masked ROM code has failed checksum test indicating that masked ROM data is no longer valid.
^ ROM code has failed checksum test indicating that ROM data is no longer valid.
^ One or more RAM locations have failed operational test indicating that some portions of RAM are not functional.
^ Motor circuit test has indicated that one of the module's relays is not able to make contact.
Action Taken When the DTC Sets
^ The SERVICE indicator (AWD/4WD) lamp will be latched on and the system will be disabled.
Conditions for Clearing the DTC
^ Replace the transfer case shift control module.
^ Perform the transfer case shift control module.
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 2 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 indicator (AWD/4WD) lamp will be latched on.
Conditions for Clearing the DTC
A history DTC will clear after a valid VIN digit is received.