Drivetrain - Transfer Case Control Module Replacement
Bulletin No.: 05-04-21-002Date: March 10, 2005
INFORMATION
Subject:
Guidelines for Replacement of Transfer Case Control Module (TCCM)
Models:
2005 and Prior Light Duty Trucks
with New Venture Gear (NVG) Transfer Case (RPOs NP1, NP4, NP8)
Dealers are replacing the TCCM unnecessarily.
Dealers are replacing the TCCM with codes stored in HISTORY only. The TCCM does not have a current fault condition when tested.
Parts reviewed at the Warranty Parts Center (WPC) have a 75% No Trouble Found (NTF) rate. The only two legitimate reasons to replace the TCCM are:
^ Diagnostic Trouble Code (DTC) C0550
^ NO Communication with a scan tool.
DTC C0550
This DTC indicates that the module has an internal fault and should be replaced.
No Communication
^ The no communication conditions referenced here are also caused by a module internal fault to a point where the module physically will not talk. A technician cannot pull DTCs from the module because it will not communicate. The module is electrically dead.
^ No communication is not to be confused with a U1026 code. This code tells the technician that the module may still be functioning but is temporarily off line. This code may be set by the Instrument Panel (IP) or the Powertrain Control Module (PCM) against the TCCM. The technician needs to figure out why the module went off line. These are typically caused by connection concerns. There is no need to replace a TCCM for a U1026 DTC.
Diagnostic Aids
^ When diagnosing a transfer case electrical control system, ALWAYS check power and ground wiring first.
^ Test the connections for intermittent or poor connections, complete plug insertion, bent pins, pushed out terminals and water contamination.
Pay particular attention to the terminal connections at the module. Spread or open terminal connections may create an intermittent contact. Do a pin drag test. Refer to the terminal testing information in the table shown.
^ After repairs are complete, ALWAYS clear DTCs from the module prior to a system function test. If codes are not cleared first, the system will not function after repair. The technician may erroneously think that the system is still down and that further repairs are needed.
Warranty
Dealers who unnecessarily replace the TCCM that are found to have No Trouble Found (NTF) at the WPC will be returned to the AVM (Area Service Manager), or the DSM (District Service Manager) in Canada, through the Regional Feedback Process and may be charged back for the repair through the WINS system.
Disclaimer