Transfer Case
DTC C0550
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC C0550
- ECU Malfunction
Circuit/System Description
This is an internal fault detection of the transfer case shift control module (TCCM). This fault is handled inside the TCCM, no external circuits are involved.
At each ignition ON, the TCCM runs an internal self-test on the following functions:
* EEPROM Checksum
* ROM Checksum
* RAM Checksum
* RAM Malfunction
Conditions for Running the DTC
* The TCCM runs the program to detect an internal condition at key ON. The only requirements are voltage and ground.
* Ignition ON.
* System voltage 10-16 V.
Conditions for Setting the DTC
* The random access memory (RAM) of the TCCM has failed an operational test indicating that some portions of RAM are not functional.
* The read only memory (ROM) or the masked ROM of the TCCM has failed the Checksum test indicating that the data is not currently valid.
* The critical operational parameters stored in the EEPROM of the TCCM have failed the Checksum test indicating invalid data.
Action Taken When the DTC Sets
* The encoder motor will be deactivated for the remainder of the current ignition cycle.
* No further mode changes shall be allowed.
* The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.
Conditions for Clearing the DTC
* The TCCM will clear the DTC once the condition for setting the DTC no longer exists.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.
* History DTCs can be cleared using a scan tool.
Diagnostic Aids
* DTC C0550 detects the wrong copy of non-volatile memory in RAM or a RAM read/write failure.
* DTC C0550 detects a non-volatile memory write error.
* DTC C0550 detects a corruption of the EPROM/Flash memory.
* When attempting to set TCCM internal DTCs, let the engine run for at least 1 minute, then shut the engine OFF for 30 seconds. Following this procedure will allow for a complete TCCM shutdown. Reprogram the TCCM and retest the DTC to see if the DTC resets.
* A low battery condition or charging system that is faulty could set this DTC. Refer to Battery Inspection/Test (Battery Inspection/Test) and Charging System Test (Charging System Test).
Reference Information
Schematic Reference
Transfer Case Control Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Transfer Case Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Engine running. Let the engine run for at least 1 minute.
2. Ignition OFF for at least 30 seconds to allow for the complete shutdown of the TCCM.
3. Ignition ON, verify that DTC C0550 is not set.
• If DTC C0550 sets, reprogram the TCCM. If the DTC resets, replace the TCCM. Perform the ATC motor learn procedure.
Circuit/System Testing
1. Key removed. Disconnect the X1 and X2 connectors at the TCCM.
2. Install the EL-49742 harness.
3. Using the L_GN probe J 35616-16, verify that a test lamp illuminates between the TCCM ground circuit, TCCM harness X1, pin 1 and the B+ terminal of the EL-49742, red terminal.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
4. Using the L_GN probe J 35616-16, verify that a test lamp illuminates between the TCCM ground circuit, TCCM harness X1, pin 9 and the B+ terminal of the EL-49742, red terminal.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
5. Using the L_GN probe J 35616-16, verify that a test lamp illuminates between the battery positive voltage circuit, TCCM harness X1, pin 8 and the ground terminal of the EL-49742, black terminal.
• If the test lamp does not illuminate test the B+ circuit for a short to ground or an open/high resistance.
6. Ignition ON. Using the L_GN probe J 35616-16, verify that a test lamp illuminates between the ignition voltage circuit, TCCM harness X2, pin 10 and the ground terminal of the EL-49742, black terminal.
• If the test lamp does not illuminate test the ignition voltage circuit for a short to ground or an open/high resistance.
7. If all circuits test normal, replace the transfer case shift control module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for transfer case shift control module replacement, setup, and programming.