For 1990-2009 cars only
Circuit Description
At each power up the transfer case shift control module runs a self test on the following:
| • | Electrically erasable programmable read only memory (EEPROM) Checksum |
| • | Read only memory (ROM) Checksum |
| • | Random access memory (RAM) Checksum |
| • | RAM Malfunction |
| • | Relay 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 9-16 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| • | Masked ROM code has failed Checksum test indicating that masked ROM data is no longer valid. |
| • | ROM code has failed Checksum test indicating that ROM data is no longer valid.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 relays is not able to make contact. |
Action Taken When the DTC Sets
| • | The SERVICE AWD indicator is illuminated for the remainder of the current ignition cycle. |
| • | All clutch activation, slip control is disabled. |
Conditions for Clearing the DTC
| • | Replace the transfer case shift control module. |
| • | Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | System OK | -- | |
