Explorer Sport Trac 4WD V8-4.6L (2008)
Principles of Operation
PRINCIPLES OF OPERATION
NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).
Vehicle communication utilizes both medium and high speed controller area network (CAN) communications. CAN is a method for transferring data
among distributed electronic modules via a serial data bus.
The vehicle is equipped with 2 module communication networks:
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Medium speed (MS) CAN
-
High speed (HS) CAN
MS-CAN
The MS-CAN is a medium speed communication network that uses an unshielded twisted pair cable of data (+) and data (-) circuits. The data (+) and
the data (-) circuits are each regulated to approximately 2.5 volts during neutral or rested network traffic. As bus messages are sent on the data (+)
circuit, voltage is increased by approximately 1.0 volt. Inversely, the data (-) circuit is reduced by approximately 1.0 volt when a bus message is sent.
Multiple bus messages can be sent over the network CAN circuits allowing multiple modules to communicate with each other. The MS-CAN will not
communicate while certain faults are present, but will operate with diminished performance with other faults present. The MS-CAN may remain
operational when 1 of the 2 termination resistors are not present.
The MS-CAN operates at a maximum data transfer speed of 125 Kbps for bus messages and designed for general information transfer. The network
will remain operational, but at a degraded level, when certain circuit faults are present.
The following modules are on the MS-CAN:
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Audio control module (ACM)
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Instrument cluster (IC)
-
Smart junction box (SJB)
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Parking aid module (PAM) (if equipped)
-
Driver seat module (DSM) (if equipped)
-
Satellite digital audio receiver system (SDARS) module (if equipped)
-
Power running board (PRB) module (if equipped)
-
Rear entertainment module (RETM) (if equipped)
-
Heating ventilation air conditioning (HVAC) module (if equipped)
The following fault chart describes the specific MS-CAN failures and their resulting symptom:
MS-CAN Communication Fault Chart
HS-CAN
The HS-CAN is a high speed communication network that uses an unshielded twisted pair cable of data (+) and data (-) circuits. The data (+) and the
