Transfer Case

DTC C0550

CIRCUIT DESCRIPTION
At each power-up the transfer case shift control module runs a self-test on the following functions:
- EEPROM Checksum
- ROM Checksum
- RAM Checksum
- RAM Malfunction

CONDITIONS FOR RUNNING THE DTC
- The ignition is ON.
- The system voltage is 9-18 volts.

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 currently valid.
- ROM code has failed Checksum test indicating that ROM data is not currently valid.
- One or more ROM locations have failed operational test indicating that some portions of RAM are not functional.

ACTION TAKEN WHEN THE DTC SETS
- The SERVICE 4WD indicator will be latched on and the system will be disabled.
- The transfer case control switch will display the current position LED while DTC C0550 is current, but further shifting will be disabled.

CONDITIONS FOR CLEARING THE DTC
- Replace the transfer case shift control module.
- Perform the Transfer Case Diagnostic System Check.

TEST DESCRIPTION

Steps 1-2:

The number below refers to the step number on the diagnostic table.
2. This step replaces the transfer case shift control module.