For 1990-2009 cars only
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC C0550: ECU MalfunctionCircuit/System 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. |
| • | 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 remains illuminated for the remainder of the current ignition cycle. |
| • | The transfer case control switch does not display the current position LED while DTC C0550 is current. |
Conditions for Clearing the DTC
| • | Replace the transfer case shift control module. |
| • | Perform the Diagnostic System Check - Vehicle . |
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Description and Operation
Transfer Case Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
