Milan FWD L4-2.3L (2008)
If the DTCs retrieved are related to the concern, go to DTC Charts. For all other DTCs, refer to Body Control Systems (Multifunction Electronic
Control Module). See: Diagnostic Trouble Code Descriptions/Module Communications Network
7. If no DTCs related to the concern are retrieved, GO to Symptom Chart. See: Symptom Related Diagnostic Procedures
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 using a serial data bus.
The vehicle is equipped with 2 module communication networks:
-
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 MS-CAN may remain operational with only one
termination resistor present.
The following modules are on the MS-CAN:
-
Accessory protocol interface module (APIM) (if equipped)
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Audio control module (ACM)
-
Audio digital signal processing (DSP) module (if equipped)
-
Driver door module (DDM) (if equipped)
-
Driver seat module (DSM) (if equipped)
-
Dual climate control seat module (DCSM) (if equipped)
-
Heating ventilation air conditioning (HVAC) module (if equipped)
-
Instrument cluster (IC)
-
Parking aid module (PAM) (if equipped)
-
Satellite digital audio receiver system (SDARS) module (if equipped)
-
Smart junction box (SJB)
The following fault chart describes the specific MS-CAN failures and their resulting symptom:
