MODULE-TRAILER TOW
DESCRIPTION
The Trailer Module (TM) (1) is used only on vehicles manufactured for certain export markets and equipped with a factory-installed trailer towing package. The TM is secured to a mounting plate within a cavity on the right side of a molded plastic intermediate step assembly located on the rear floor panel under the second row seat cushion. The module is concealed beneath a carpeted trim cover secured by hook and loop fasteners over the step cavity. The outboard side of this step cavity also contains the intrusion module on vehicles that are so equipped. The TM is connected to the vehicle electrical system through dedicated take outs and connectors of the body wire harness.
There are two mounting tabs (2) integral to the TM housing are secured by two nuts to two studs integral to the mounting plate. Four connector receptacles (4) containing terminal pins that connect the module to the vehicle electrical system are integral to the one side of the housing. One additional receptacle (3) is not utilized in this application.
The TM cannot be adjusted or repaired and, if damaged or ineffective, it must be replaced.
OPERATION
The microprocessor within the Trailer Module (TM) contains the trailer tow lighting and electrical control logic circuits. The module uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool using the Controller Area Network (CAN) data bus. This method of communication is also used for trailer tow lighting and electrical control system diagnosis and testing through the 16-way data link connector located on the driver side lower edge of the instrument panel.
Pre-programmed decision algorithms allow the TM microprocessor to determine the appropriate trailer tow electrical control outputs based upon hard wired inputs from the brake lamp switch and the ignition switch as well as from electronic message inputs received from the Front Control Module (FCM) over the CAN data bus. When the programmed conditions are met, the TM provides voltage to the appropriate trailer tow lighting and electrical control circuits. These circuits feed the trailer circuits through dedicated trailer tow wiring in the vehicle and the trailer tow connector on the trailer hitch platform.
The TM also continuously monitors the resistance through each of these electrical output circuits, which allows the module logic circuits to detect problems and determine the system readiness. If the module detects a monitored system fault, it sets a Diagnostic Trouble Code (DTC) and sends the appropriate electronic messages to the FCM over the CAN data bus. The FCM responds to these messages by increasing the flash rate of the turn signal circuits and transmitting electronic messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN. The EMIC then provides feedback to the vehicle operator by increasing the flash rate of the turn signal indicators and increasing the click rate of a solid state relay that emulates the audible output of an electromechanical turn signal flasher.
The TM receives battery current on a fused B(+) circuit and a fused ignition switch output (run-start) circuit through fuses in the Junction Block (JB). The module receives ground through a ground circuit and take out of the body wire harness. These connections allow the module to be operational regardless of the ignition switch position.
The hard wired inputs and outputs of the TM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the TM or the electronic controls or communication between modules and other devices that provide some features of the trailer tow lighting system. The most reliable, efficient, and accurate means to diagnose the TM or the electronic controls and communication related to TM operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
REMOVAL
1. Disconnect and isolate the battery negative cable.
2. Fold and tumble the right outboard second row seat assembly forward.
3. Remove the carpeted cover panel from over the cavity on the right outboard end of the intermediate step assembly (4).
4. Disconnect the four body wire harness connectors from the connector receptacles (2) on the back of the Trailer Module (TM) (3).
5. Remove the two nuts (6) that secure the TM to the studs on the mounting plate (5) on the floor of the step cavity.
6. Remove the module from the mounting plate.
INSTALLATION
1. Position the Trailer Module (TM) (3) over the two studs integral to the mounting plate (5) on the floor of the right cavity of the intermediate step assembly (4).
2. Install and tighten the two nuts (6) that secure the module to the mounting plate studs. Tighten the nuts to 1 N·m (15 in. lbs.).
3. Reconnect the four body wire harness connectors to the module connector receptacles (2).
4. Reinstall the carpeted cover panel over the cavity on the right outboard end of the intermediate step assembly.
5. Restore the right outboard second row seat assembly to its normal seating position.
6. Reconnect the battery negative cable.