Module Communications Network: Other Ford Focus II facelift

Network Termination

The CAN 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.

SPECIAL TOOLS - COMMUNICATIONS NETWORK 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

Scheme 66

Scheme 67

HS-CAN and MS-CAN

CAN is a 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 operates at a maximum data transfer speed of 125 Kbps for bus messages and is designed for general information transfer. The HS-CAN operates at a maximum data transfer speed of 500 Kbps and is designed for real time information transfer and control.

Certain network faults may cause inconsistent message communication. The CAN may remain operational with only 1 of the 2 termination resistors present.

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

CAN COMMUNICATION FAULT CHART

The following chart describes the specific HS-CAN messages broadcast by each module, and the module(s) that receive the message

Note. Network DTCs which are not listed in the below chart either relate to an invalid data concern (the message is not missing but the data value sent not within acceptable range) or indicate an entire network bus outage concern which is not specifically related to missing data from certain modules, i.e. the network is open or shorted. Refer to DTC Charts for specific DTC information and recommended action.

HS-CAN MODULE COMMUNICATION MESSAGE CHART