MP 1625/1626-NQF - Transfer Case

DTC C0550

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC C0550 37
- Electronic Control Unit Malfunction Watchdog/Safety Failure

DTC C0550 39
- Electronic Control Unit Malfunction Internal Electronic Failure




Diagnostic Fault Information






Circuit/System Description

This DTC indicates and RAM/ROM checksum, a EEPROM failure, or an ECU malfunction due to an internal microprocessor failure.


Conditions for Running the DTC

* The ignition is ON.
* System voltage is 10.5-18 volts.



Conditions for Setting the DTC

The EEPROM, RAM and ROM, and ECM Microprocessor do self checks against one another and the data does not match causing the DTC to set.


Action Taken When the DTC Sets

* Shifting is still disabled until the DTC has cleared itself.
* The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.



Conditions for Clearing the DTC

* The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
* A history DTC clears after 40 consecutive warm up cycles without a fault present.
* History DTCs can be cleared using a scan tool.



Reference Information
Schematic Reference

Transfer Case Control Schematics (MP 1625/1626-NQF - Transfer Case)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information.


Diagnostic Aids

It is sometimes possible to set this DTC falsely due to low voltage. Attempt to clear this DTC and retest.


Circuit/System Testing

1. If this DTC sets attempt to clear the DTC and Retest.
2. If the DTC is cleared, but then resets then replace the transfer case control module, program, and complete the transfer case motor learn procedure.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Module References (Programming and Relearning) for TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset)