Engine Controls - Erroneous DTC's Set
NUMBER: 08-003-04GROUP: Electrical
DATE: January 6, 2004
SUBJECT:
Erroneous Diagnostic Trouble Codes (DTC's)
MODELS:
2004 (HB) Durango
DISCUSSION:
The 2004 Durango may have erroneous DTC's due to the following:
^ Ignition Off Draw (IOD) fuse cartridge being removed.
^ The ignition switch position.
^ The Controller Area Network (CAN) in sleep mode.
NOTE:
The following list of DTC's may be erroneous or valid based on vehicle circumstances (see "DETAILS - ERRONEOUS DTC's)". All other DTC's displayed on the StarSCAN tool are valid.
Summary of Erroneous DTC's
NOTE:
DTC's can be read using the StarSCAN tool using the "ECU View" from the "Home" screen.
DETAILS - ERRONEOUS DTC'S Ignition Switch Induced Erroneous DTC's:
^ "B106B - Rear Defrost Control Circuit Low"
^ "U0121 - Lost Communication with Anti-Lock Brake System (ABS)"
Erroneous "Stored" DTC's can be set in the Front Control Module (FCM) due to the positioning of the ignition switch. When the ignition switch is rotated slowly into a position between "Run" and "Off", the ABS module and the Rear Defrost Control Relay lose power. If this situation occurs, the FCM will set DTC's B106B and U0121.
Mature Times:
^ B106B will be set if the FCM detects an open condition on the Rear Defrost Control Circuit for 2 seconds or more.
^ U0121 will be set if the FCM does not receive messages from the ABS module for 0.5 seconds or more.
Service Action:
^ If either of these "Stored" DTC's (B106B and U0121) is present in the FCM, they should be ignored.
^ If either of these DTC's (B106B and U0121) are "Active" in the FCM while the ignition switch is in the "RUN" position, they should be considered valid and normal diagnostic procedures should be performed.
IOD Fuse Induced Erroneous DTC's:
The 2004 HB has two (2) 30 amp IOD fuses installed in a fuse cartridge located under the hood in the Integrated Power Module (IPM). The dealership is required to engage the IOD fuse cartridge prior to customer delivery. This IOD fuse cartridge has both primary and secondary engagement latches. When engaging the IOD fuse cartridge, the technician must push the cartridge down fully past both engagement latches to properly seat the fuses. If the IOD fuse cartridge is not properly seated or is removed, certain "Active" DTC's may be set in modules on the vehicle. In addition, certain "Stored" DTC's may be present from a previous IOD fuse removal either from assembly plant shipping or previous vehicle service.
Two different types of DTC's can be set as a result of the IOD fuse cartridge removal, Heating, Ventilation, & Air Conditioning (HVAC) DTC's and CAN Lost Communication DTC's.
HVAC DTC's Erroneous "Stored" DTC's:
^ "B108E - Infrared Temperature Sensor Internal"
^ "B108F - Automatic Temperature Control System Performance"
Either or both of the DTC's may be set in Automatic Temperature Control (ATC) HVAC module when the IOD fuse cartridge is removed and then reinstalled. These DTC's are set as a pair when the ATC module loses the infrared (IR) signal from the Electronic Overhead Module (EOM). A valid loss of the IR signal can be further confirmed as the ATC module will be in a default mode, only allowing manual control (no Auto mode).
Service Action:
^ If either or both of these "Stored" DTC's (B108E and B108F) are present, they should be ignored unless there are additional DTC's or functional issues present with the HVAC system on the vehicle.
^ If there is a related customer concern with the HVAC system, the DTC's should be erased. If the DTC's return after being erased with the IOD fuse cartridge installed, there is a valid concern that should be diagnosed using the normal diagnostic procedures.
IOD Fuse Induced CAN Lost Communication Erroneous DTC's:
An enhanced loss of communication diagnostic strategy has been implemented on the 2004 HB to aid technicians in troubleshooting vehicle CAN network (bus) concerns. This strategy is similar to what exists on PCI (J1850 bus) vehicles, but the CAN strategy was enhanced to include monitoring for all modules on the vehicle. Each module in the vehicle monitors most of the other modules on the bus, and reports a "Lost Communication with Module "X"" DTC for any module that stops communicating when communication is expected (Fig. 1).
The CAN lost communication diagnostic strategy is very powerful, but due to some minor deviations of diagnostic requirements, some modules incorrectly set certain lost communication DTC's while the IOD fuse cartridge is removed.
Some modules are powered by the IOD fuses while others are not. Since only some modules will be powered while the IOD fuse cartridge is removed, erroneous lost communication DTC's (DTC's beginning with "U") can be set. This situation will occur when the IOD fuse cartridge is removed when the vehicle is shipped from the assembly plant or if removed during vehicle service. IOD induced DTC's on their own do not constitute a true failure on the CAN network system or vehicle. Once the IOD fuse cartridge is installed the DTC status for lost communication DTC's should change to "Stored". All "Stored" DTC's will be self-erased by the module after 100 consecutive ignition key cycles. "Active" lost communication DTC's indicate valid vehicle concerns and should be used to identify the root cause of the failure(s).
NOTE:
The StarSCAN tool will not communicate with the vehicle if the IOD fuse is not present.
Mature Times:
^ Most lost communication DTC's mature within 0.5 seconds.
Service Action:
^ If "Stored" lost communication DTC's are present during vehicle preparation and other DTC's or functional issues are NOT present in modules on the vehicle, these DTC's should be ignored.
^ If "Active" lost communication DTC's are present, there is a valid concern that should be diagnosed using the normal diagnostic procedures.
NOTE:
"DTC Environmental Data" can be read from the StarSCAN tool to determine the mileage when each DTC was set. This can be used to aid in determining if the lost communication DTC's are associated to the removal of the IOD fuse cartridge at the vehicle assembly plant.
Sleep Induced CAN Network Erroneous DTC'S:
The CAN-B vehicle network is designed to operate both in the ignition run and ignition off state. When data is not needed by any of the modules, the CAN-B network will go to sleep and messages will no longer be transmitted.
Erroneous "Active" DTC's:
^ "U0141 - Lost Communication with Front Control Module (FCM)"
^ "U0155 - Lost Communication with Cluster/CCN"
Either or both of the DTC's may be set in the Electronic Overhead Module (EOM) when the CAN-B network goes to sleep. These DTC's will only be present on the StarSCAN scan tool if other modules also have U0141 or U0155 DTC's present.
Service Action:
^ If either or both of these "Active" DTC's (U0141 and U0155) are present in the EOM, they should always be ignored.
^ If other modules have either of these "Active" DTC's (U0141 and U0155) present, normal vehicle diagnostic procedures should be followed
^ If other modules have either of these "Stored" DTC's (U0141 and U0155) present, normal vehicle diagnostic procedures should be followed.
POLICY:
Information Only
Disclaimer:
This bulletin is supplied as technical information only and is not an authorization for repair.