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Communications Network: Notes

NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).

Vehicle communication utilizes both high speed (HS) and medium speed (MS) controller area network (CAN) communications. CAN in-vehicle networking, is a method for transferring data among distributed electronic modules via a serial data bus. Without serial networking, intermodule communication requires dedicated, point to point wiring resulting in bulky, expensive, complex, and difficult to install wiring harnesses. Applying a serial data network reduces the number of wires combining the signals on a single network. Information is sent to individual control modules that control each function.

The vehicle has 2 module communication networks:

Both networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one scan tool to be able to diagnose and control any module on both networks from one connector. The DLC can be found under the instrument panel.

Fig 1: Identifying High Speed CAN & Medium Speed CAN
GF0043652Courtesy of FORD MOTOR CO.
Module Name Network Type Termination Module
ABS HS-CAN No
Accessory protocol interface module (APIM) (if equipped) HS-CAN/MS-CAN No
Audio control module (ACM) MS-CAN No
Front controls interface module (FCIM) MS-CAN No
Front display interface module (FDIM) MS-CAN No
HVAC module (if equipped) MS-CAN No
Instrument cluster (IC) (gateway module) HS-CAN
MS-CAN
Yes
Yes
Occupant classification system module (OCSM) HS-CAN No
PCM HS-CAN Yes
Restraints control module (RCM) HS-CAN No
Satellite digital audio receiver system (SDARS) module (if equipped) MS-CAN No
Smart junction box (SJB) MS-CAN Yes