Module Communications Network -- Electric: Other Ford Focus III

Network Termination

The CAN uses network termination to improve communication reliability. Termination modules are located at both ends of the 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 an internal 120 ohm resistor that bridges across the positive and negative bus connection. With two 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 Modules

The GWM is mounted under the driver's side instrument panel. The GWM acts as a central gateway to translate messages for the 3 high speed vehicle CAN networks, and vice versa. It acts as a gateway for messages on the Electric Vehicle (EV) High Speed CAN to the other 2 High Speed CAN .

The BCM is also a gateway module. The BCM translates messages on the High Speed CAN to the Medium Speed CAN and vice versa. This allows a message to be distributed throughout all applicable networks.

The BCM and GWM are the only modules on this vehicle that have this ability.

High Speed Controller Area Network (HS-CAN)

The High Speed Controller Area Network (HS-CAN) operates at a maximum data transfer speed of 500 Kbps and is designed for real time powertrain information transfer and control.

Modules on the High Speed Controller Area Network (HS-CAN) communicate using bussed messages. The High Speed Controller Area Network (HS-CAN) uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, the High Speed Controller Area Network (HS-CAN) allows sharing of information between all modules on the network.

Electric Vehicle (EV) High Speed Controller Area Network (HS-CAN)

The Electric Vehicle (EV) High Speed Controller Area Network (HS-CAN) operates at a maximum data transfer speed of 500 Kbps and is designed for real time powertrain information transfer and control, specific for the battery electric vehicles.

Modules on the Electric Vehicle (EV) High Speed Controller Area Network (HS-CAN) communicate using bussed messages. The Electric Vehicle (EV) High Speed Controller Area Network (HS-CAN) uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, the Electric Vehicle (EV) High Speed Controller Area Network (HS-CAN) allows sharing of information between all modules on the network.

Medium Speed Controller Area Network (MS-CAN)

The Medium Speed Controller Area Network (MS-CAN) operates at a maximum data transfer speed of 125 Kbps and is designed for general information transfer.

Modules on the Medium Speed Controller Area Network (MS-CAN) communicate using bussed messages. The Medium Speed Controller Area Network (MS-CAN) uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, the Medium Speed Controller Area Network (MS-CAN) allows sharing of information between all modules on the network.

Infotainment Controller Area Network (I-CAN)

The Infotainment Controller Area Network (I-CAN) operates at a maximum data transfer speed of 500 Kbps and is designed for real time audio and multimedia information transfer and control.

Modules on the Infotainment Controller Area Network (I-CAN) communicate using bussed messages. Infotainment Controller Area Network (I-CAN) uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. The Infotainment Controller Area Network (I-CAN) allows sharing of information between all modules on the network.

The Infotainment Controller Area Network (I-CAN) is connected to the DLC , but the Infotainment Controller Area Network (I-CAN) modules communicate with the scan tool over the High Speed Controller Area Network (HS-CAN). The GWM is used as a gateway for the messages to transfer between the scan tool and the modules on the Infotainment Controller Area Network (I-CAN).

Controller Area Network (CAN) Fault Tolerance

Note. The oscilloscope traces shown are from the IDS oscilloscope taken using the IDS pre-configured CAN settings. The traces are for both data (+) and data (-) taken simultaneously (2-channel) at a sample rate of 1 mega-sample per second (1MS/s) or greater.

Scheme 18

The data (+) and data (-) circuits are each regulated to approximately 2.5 volts during neutral or rested network traffic. As 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 message is sent.

Successful communication of a message can usually be identified by the slight spike at the end of a message transmission. Any signals that are significantly different than the normal CAN waveform may cause network Diagnostic Trouble Codes (DTCs) (U-codes) to set or may cause a complete network outage.

Scheme 19

In the event the data (+) and data (-) circuits become shorted together, the signal stays at base voltage (2.5V) continuously and all communication capabilities are lost.

Scheme 20

In the event the data (+) circuit becomes shorted to ground, both the data (+) and data (-) circuits are pulled low (0V) and all communication capabilities are lost.

Scheme 21

In the event the data (-) circuit becomes shorted to ground, the data (-) circuit is pulled low (0V) and the data (+) circuit reaches near-normal peak voltage (3.0V) during communication but falls to 0V instead of normal base voltage (2.5V). Communication may continue but at a degraded level.

Scheme 22

In the event the data (+) circuit becomes shorted to battery voltage, the data (+) circuit is pulled high (12V) and the data (-) circuit falls to abnormally high voltage (above 5V) during communication and reaches battery voltage (12V) for peak voltage. Communication may continue but at a degraded level.

Scheme 23

In the event the data (-) circuit becomes shorted to battery voltage, both the data (+) and data (-) circuits are pulled high (12V) and all communication capabilities are lost.

Scheme 24

Rhythmic oscillations, inductive spikes or random interference can corrupt the network communications. The corruption signal source may be outside electrical interference such as motors or solenoids or internal interference generated from a module on the network. In some cases, an open in either the data (+) or data (-) circuit to a network module may cause the module to emit interference on the one circuit which is still connected. The trace shown is an example of a "sawtooth" pattern transmitted from a module with one open network circuit.

Other corruptions may be present when a module is intermittently powered up and down. The module on power up may initiate communication out of sync with other modules on the network causing momentary communication outages.

Controller Area Network (CAN) Multiplex Messages

COMMUNICATION MESSAGE CHART

Possible Sources

1. Fuse
2. Wiring, terminals and connectors
3. PCM

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

Possible Causes

1. Fuse
2. Wiring, terminals and connectors
3. RCM

1. Fuse
2. Wiring, terminals and connector
3. OCSM

1. Fuse
2. Wiring, terminals and connector
3. SASM

1. Fuse
2. Wiring, terminals and connector
3. IPC

1. Fuse
2. Wiring, terminals and connector
3. BCM

1. Fuse
2. Wiring, terminals and connector
3. HVAC module

1. Fuse
2. Wiring, terminals and connector
3. ACM

1. Fuse
2. Wiring, terminals and connector
3. DDM

1. Fuse
2. Wiring, terminals and connector
3. PDM

1. Fuse
2. Wiring, terminals and connector
3. Image Processing Module - B (IPM-B)

1. Fuse
2. Wiring, terminals and connector
3. Parking Aid Module (PAM)

1. Fuse
2. Wiring, terminals and connector
3. APIM

1. Fuse
2. Wiring, terminals and connector
3. FCIM

1. Fuse
2. Wiring, terminals and connector
3. RFA module

1. Fuse
2. Wiring, terminals and connector
3. TCM

1. Fuse
2. Wiring, terminals and connector
3. PSCM

1. Fuse
2. Wiring, terminals and connector
3. TCU

1. Fuse
2. Wiring, terminals and connector
3. BECM

1. Fuse
2. Wiring, terminals and connectors
3. SOBDM

1. Fuse
2. Wiring, terminals and connector
3. ACCM

1. Fuse
2. Wiring, terminals and connectors
3. Direct Current/Direct Current (DC/DC) Converter Control Module

1. Fuse
2. Wiring, terminals and connector
3. GFM

1. Fuse
2. Wiring, terminals or connectors
3. APIM
4. BCM
5. GWM
6. OCSM
7. Parking Aid Module (PAM)
8. PSCM
9. SASM
10. RCM

1. Fuse
2. Wiring, terminals or connectors
3. ABS Module
4. ACCM
5. BECM
6. Direct Current/Direct Current (DC/DC) Converter Control Module
7. GWM
8. GFM (Charge Port Light Ring)
9. PCM
10. SOBDM
11. TCM

1. Fuse
2. Wiring, terminals or connectors
3. APIM (if equipped)
4. BCM
5. DDM
6. GPSM
7. HVAC Module
8. Image Processing Module-B (IPM-B)
9. IPC
10. PDM
11. RFA Module

1. Fuse
2. Wiring, terminals or connectors
3. ACM
4. APIM
5. IPC
6. FCIM
7. GWM
8. TCU

1. Fuse
2. Wiring, terminals or connector
3. DLC
4. Scan tool

A loss of ground or poor ground at the DLC may result in High Speed Controller Area Network (HS-CAN), Electric Vehicle (EV) High Speed Controller Area Network (HS-CAN), Medium Speed Controller Area Network (MS-CAN) or Infotainment Controller Area Network (I-CAN) faults while the scan tool is connected.

Activation