For 1990-2009 cars only
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| • | Masked ROM code has failed Checksum test indicating that masked ROM data is no longer valid.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| • | ROM code has failed Checksum test indicating that ROM data is no longer valid.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's relays is not able to make contact. |
Action Taken When the DTC Sets
The SERVICE 4WD indicator will be latched on and the system will be disabled.
Conditions for Clearing the DTC
| • | Replace the transfer case shift control module. |
| • | Perform the Transfer Case Diagnostic System Check. |
Test Description
The number below refers to the step number on the diagnostic table
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics | |||
1 | Was the Transfer Case Diagnostic System Check performed? | Go to Step 2 | |
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement . Is the repair complete? | System OK | -- | |
