Module Communications Network: Overview Ford Expedition III

Note. The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. Multiplexing is used to allow 2 or more electronic modules (nodes) to communicate simultaneously over a twisted-wire pair [data (+) and data (-)] network. The information or messages that can be communicated on these wires consists of commands, status or data. The advantage of using multiplexing is to reduce the weight of the vehicle by reducing the number of redundant components and electrical wiring.

The vehicle has 2 module communication networks which are connected to the Data Link Connector (DLC), located under the instrument panel

1. High Speed Controller Area Network (HS-CAN)
2. Medium Speed Controller Area Network (MS-CAN)

Scheme 1

COMMUNICATIONS NETWORK CHART

Principles of Operation

Note. The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

Both the High Speed Controller Area Network (HS-CAN) and the Medium Speed Controller Area Network (MS-CAN) use an unshielded twisted-pair cable of data (+) and data (-) circuits. The HS-CAN operates at a maximum data transfer speed of 500 Kbps and is designed for real time information transfer and control. The MS-CAN operates at a maximum data transfer speed of 125 Kbps for bus messages and is designed for general information transfer.

Normal Operation

The PCM communicates with the scan tool through the High Speed Controller Area Network (HS-CAN).

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. PCM

The ABS module communicates with the scan tool through the High Speed Controller Area Network (HS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. ABS module

The Instrument Cluster (IC) communicates with the scan tool and other modules through the High Speed Controller Area Network (HS-CAN). The IC communicates with other modules on the HS-CAN and the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. IC

The Restraints Control Module (RCM) communicates with the scan tool through the High Speed Controller Area Network (HS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Case ground open
4. RCM

The 4X4 control module communicates with the scan tool through the High Speed Controller Area Network (HS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. 4X4 control module

The Vehicle Dynamics Module (VDM) communicates with the scan tool through the High Speed Controller Area Network (HS-CAN). ( HS-CAN +) and ( HS-CAN -) provide the network connection to the VDM .

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. VDM

The Transmission Control Module (TCM) communicates with the scan tool through the High Speed Controller Area Network (HS-CAN). ( HS-CAN +) and ( HS-CAN -) provide the network connection to the TCM .

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. TCM

The Smart Junction Box (SJB) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. SJB

The HVAC module communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. HVAC module

The Liftgate/Trunk Module (LTM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuses
2. Wiring, terminals or connectors
3. LTM

The Audio Control Module (ACM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. ACM

The audio Digital Signal Processing (DSP) module communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuses
2. Wiring, terminals or connectors
3. Audio DSP module

The Satellite Digital Audio Receiver System (SDARS) module communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. SDARS module

The audio Rear Control Unit (RCU) module communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Audio RCU module

The Rear Entertainment Module (RETM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. RETM

The Driver Seat Module (DSM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. DSM

The Dual Climate Controlled Seat Module (DCSM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN). ( MS-CAN +) and ( MS-CAN -) provide the network connection to the DCSM .

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. DCSM

The Power Running Board (PRB) module communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. PRB module

The Parking Aid Module (PAM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. PAM

The Accessory Protocol Interface Module (APIM) communicates with the scan tool through the High Speed Controller Area Network (HS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. APIM

The Global Positioning System Module (GPSM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. GPSM

The Medium Speed Controller Area Network (MS-CAN) uses an unshielded twisted pair cable. ( HS-CAN +) and ( HS-CAN -) provide the network connection to all modules on the network.

In the event that 1 of the 2 network circuits ( MS-CAN + or MS-CAN -) becomes open to a module on the network, unreliable network communication to all modules on the network may result.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors

The Medium Speed Controller Area Network (MS-CAN) uses an unshielded twisted pair cable, circuits VDB06 (GY/OG) and VDB07 (VT/OG) provide the network connection to all modules on the network.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. Audio Control Module (ACM)
3. Accessory Protocol Interface Module (APIM)
4. Audio Digital Signal Processing (DSP) module (if equipped)
5. Audio Rear Control Unit (RCU) module (if equipped)
6. Dual Climate Controlled Seat Module (DCSM) (if equipped)
7. Driver Seat Module (DSM) (if equipped)
8. Global Positioning System Module (GPSM)
9. HVAC module (if equipped)
10. Instrument Cluster (IC)
11. Liftgate/Trunk Module (LTM) (if equipped)
12. Parking Aid Module (PAM) (if equipped)
13. Power Running Board (PRB) module (if equipped)
14. Rear Entertainment Module (RETM) (if equipped)
15. Satellite Digital Audio Receiver System (SDARS) module (if equipped)
16. Smart Junction Box (SJB)
17. Data Link Connector (DLC)

The High Speed Controller Area Network (HS-CAN) uses an unshielded twisted pair cable, (HS-CAN+) and (HS-CAN-).

In the event that 1 of the 2 network circuits (HS-CAN+ or HS-CAN-) becomes open to a module on the network, unreliable network communication to all modules on the network may result.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. Data Link Connector (DLC)

The High Speed Controller Area Network (HS-CAN) uses an unshielded twisted pair cable.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. Data Link Connector (DLC)
3. 4X4 control module (if equipped)
4. ABS module
5. Accessory Protocol Interface Module (APIM)
6. Instrument Cluster (IC)
7. PCM
8. Restraints Control Module (RCM)
9. Transmission Control Module (TCM)
10. Vehicle Dynamics Module (VDM) (if equipped)

The scan tool is connected to the Data Link Connector (DLC) to communicate with the High Speed Controller Area Network (HS-CAN) and the Medium Speed Controller Area Network (MS-CAN) communications network.

A loss of ground or poor ground at the DLC may result in HS-CAN or MS-CAN faults while the scan tool is connected.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Data Link Connector (DLC)
4. Scan tool

See also:
• AUTOMATIC TRANSAXLE/TRANSMISSION - 6R80
• SEATING