For 1990-2009 cars only
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 |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0550 ECU 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 Diagnostic System Check - Vehicle . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Replace the transfer case shift control module. Refer to Control Module References for replacement, setup and programming. Is the repair complete? | System OK | -- | |
