MP 1625/1626-NQF - 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 37
- Electronic Control Unit (ECU) Performance Watchdog Failure
DTC C0550 39
- Electronic Control Unit (ECU) Internal Electronic Failure
Diagnostic Fault Information
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 power-up, the TCCM runs a self-test on the following:
* 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 10.5-18 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.
* The transfer case shift control switch will illuminate the current mode position LED.
* No further mode changes shall be allowed.
* The TCCM will store freeze frame data.
* 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 conditions for setting the DTC no longer exist.
* A history DTC will clear after 40 consecutive warm up cycles without a fault present.
* History DTCs can be cleared using a scan tool.
Diagnostic Aids
* DTC P0550 detects the wrong copy of non-volatile memory in RAM or a RAM read/write failure.
* DTC P0550 detects a non-volatile memory write error.
* DTC P0550 detects a corruption of the EPROM/Flash memory.
* When attempting to set TCCM internal DTCs, let the engine run for at least 1 minute and 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 voltage condition can sometimes falsely set this DTC. Attempt to clear this DTC and retest.
Reference Information
Schematic Reference
Transfer Case Control Schematics (MP 1625/1626-NQF - Transfer Case)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Transfer Case Description and Operation (Transfer Case 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)
Scan Tool Reference
Control Module References (Control Module References) 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.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control Module References (Control Module References) for TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset)