NVG 136-NP4 (One Speed Automatic)

DTC C0550






DTC C0550 ECU Malfunction

Circuit Description
At each power up the transfer case shift control module runs a self test on the following:
^ EEPROM Checksum
^ ROM Checksum
^ RAM Checksum
^ RAM Malfunction
^ Relay 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 not valid.
^ ROM code has failed Checksum test indicating that ROM data is not valid.
^ One or more ROM locations have failed operational test indicating that some portions of RAM are not functional.
^ Motor circuit test has indicated that one of the modules's relays is not able to make contact.

Action Taken When the DTC Sets
The SERVICE indicator (4WD/AWD) 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 Diagnostic System Check Transfer Case.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Replacement of the transfer case shift control module.