Module Communications Network: Other Mercury Milan I

Network Termination

The CAN network uses a network termination circuit to improve communication reliability. The network termination of the CAN bus takes place inside the termination modules by termination resistors. Termination modules are located at either end of the bus network. As network messages are broadcast in the form of voltage signals, the network voltage signals are stabilized by the termination resistors. Each termination module has a 120 ohm resistor across the positive and negative bus connection in the termination module. With 2 termination modules on each network and the 120 ohm resistors located in a parallel circuit configuration, the total network impedance, or total resistance, is 60 ohms.

Network termination improves bus message reliability by

1. stabilizing bus voltage.
2. eliminating electrical interference.

Gateway Module

The instrument cluster is the gateway module, translating HS-CAN to MS-CAN and vice versa. This information allows a message to be distributed throughout both networks. The instrument cluster is the only module on this vehicle that has this ability.

Special Tools Illustration Tool Name Tool Number 73III Automotive Meter 105-R0057 or equivalent Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool Flex Probe Kit 105-R025C or equivalent Diagnostic Tool, Restraint System 418-133

Scheme 66

Scheme 67

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 network will not communicate while certain faults are present, but will operate with diminished performance with other faults present. The MS-CAN network may remain operational when 1 of the 2 termination resistors are not present.

The MS-CAN network 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 network may remain operational with only one termination resistor present.

The following modules are on the MS-CAN network

1. Smart junction box (SJB)
2. Instrument cluster
3. Audio unit
4. THX® amplifier (if equipped)
5. Satellite radio receiver (if equipped)
6. Electronic automatic temperature control (EATC) module (if equipped)
7. Dual automatic temperature control (DATC) module (if equipped)
8. Driver seat module (DSM) (if equipped)
9. Driver door module (DDM) (if equipped)
10. Climate controlled seat module (if equipped)

The following fault chart describes the specific MS-CAN network failures and their resulting symptom

MS-CAN NETWORK 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 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 HS-CAN network will not communicate while certain faults are present, but will operate with diminished performance with other faults present. The HS-CAN bus may remain operational when 1 of the 2 termination resistors are not present.

The HS-CAN network operates at a maximum data transfer speed of 500 Kbps and is designed for real time information transfer and control. The network will remain operational, but at a degraded level when certain circuit faults are present. The HS-CAN network may remain operational with only one termination resistor present.

The following modules are on the HS-CAN network

1. Powertrain control module (PCM)
2. Transmission control module (TCM)
3. Anti-lock brake system (ABS) module
4. Restraints control module (RCM)
5. Occupant classification sensor module
6. Instrument cluster
7. Four wheel drive (4WD) control module (if equipped)

The following fault chart describes the specific HS-CAN network failures and their resulting symptom

HS-CAN NETWORK COMMUNICATION FAULT CHART

Note. This chart describes the specific high speed controller area network (HS-CAN) and medium speed controller area network (MS-CAN) messages broadcast by each module, and the module(s) that receive the message.

CAN NETWORK MODULE COMMUNICATION MESSAGE CHART