Module Communications Network: Overview Ford Focus I facelift

Vehicle communication utilizes both International Standards Organization (ISO) 9141 and controller area network (CAN) communications. ISO 9141 is used for diagnostic use only, and CAN is used for many modules to communicate with each other on a common network. CAN in-vehicle networking, is a method for transferring data among distributed electronic modules via a serial data bus. Without serial networking, intermodule communication requires dedicated, point to point wiring resulting in bulky, expensive, complex, and difficult to install wiring harnesses. Applying a serial data network reduces the number of wires combining the signals on a single network. Information is sent to individual control modules that control each function.

The vehicle has 2 module communication networks

1. ISO 9141
2. High speed (HS) CAN

Both networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one scan tool to be able to diagnose and control any module on both networks from one connector. The DLC can be found under the instrument panel.

Scheme 1

International Standards Organization (ISO) 9141 Network Operation

The ISO 9141 communications network is a single wire network. The ISO 9141 communication network is used only by the GEM.

High Speed Controller Area Network (HS-CAN) Operation

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

The HS-CAN is a high speed communication network used for the following modules

1. PCM
2. ABS module
3. RCM
4. OCSM
5. IC

Principles of Operation

Vehicle communication utilizes both International Standards Organization (ISO) 9141 and controller area network (CAN) communications. ISO 9141 is used for diagnostic use only, and CAN is a method for transferring data among distributed electronic modules via a serial data bus.

The vehicle is equipped with 2 communication networks

1. ISO 9141
2. High speed (HS) CAN

Normal Operation

The PCM communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits 4-EC7 (GY/RD) (HS-CAN +) and 5-EC7 (BU/RD) provide the network connection to the PCM. The PCM shares the HS-CAN with the ABS module, the restraints control module (RCM), the occupant classification system module (OCSM), and the instrument cluster (IC). Circuit 30-RE8 (RD) provides voltage, and redundant circuits 91-RE8 (BK/YE) provide ground.

Possible Causes

1. Fuse
2. Circuit 30-RE8 (RD) open
3. Circuit 91-RE8 (BK/YE) open
4. Circuit 4-EC7 (GY/RD) open, short to ground or voltage (HS-CAN +)
5. Circuit 5-EC7 (BU/RD) open, short to ground or voltage (HS-CAN -)
6. Circuit 4-EC7 (GY/RD) (HS-CAN +) and circuit 5-EC7 (BU/RD) (HS-CAN -) shorted together
7. PCM
8. ABS module
9. RCM
10. OCSM
11. IC

The generic electronic module (GEM) communicates with the scan tool through circuit 8-EE9 (WH/GN). Voltage and ground for the GEM is provided by redundant circuits. Circuits 29-AA17 (OG/WH) and 29-DK20 (OG/GN) provide voltage, and circuits 91-DK20 (BK/RD) and 31-DK20 (BK) provide ground.

Possible Causes

1. Fuse
2. Circuit 8-EE9 (WH/GN) open, short to ground or voltage
3. Circuit 29-AA17 (OG/WH) open
4. Circuit 29-DK20 (OG/GN) open
5. Circuit 31-DK20 (BK) open
6. Circuit 91-DK20 (BK/RD) open
7. GEM

The restraints control module (RCM) communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits 4-EC18 (GY/BK) (HS-CAN +) and 5-EC18 (BU/BK) (HS-CAN -) provide the network connection to the RCM. The RCM module shares the HS-CAN with the PCM, the ABS module, the occupant classification system module (OCSM), and the instrument cluster (IC). Voltage for the RCM is provided by circuit 15-JA10 (GN/OG), and the RCM is case grounded.

Possible Causes

1. Fuse
2. Circuit 4-EC18 (GY/BK) open (HS-CAN +)
3. Circuit 5-EC18 (BU/BK) open (HS-CAN -)
4. Circuit 15-JA10 (GN/OG) open
5. Case ground open
6. RCM

The ABS module communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits 4-EC9 (GY) (HS-CAN +) and 5-EC9 (BU) (HS-CAN -) provide the network connection to the ABS module. The ABS module shares the HS-CAN with the PCM, the restraints control module (RCM), the occupant classification system module (OCSM), and the instrument cluster (IC). Voltage and ground for the ABS module is provided by redundant circuits. Voltage is supplied through circuit 15-CF6 (GN/YE). Ground is provided through circuits 31-CF6 (BK) and 31-CF13 (BK) (with traction control).

DTC U2012 (ABS module) - sets when the HS-CAN bus performance is compromised.

Possible Causes

1. Fuse(s)
2. Circuit 4-EC9 (GY) open (HS-CAN +)
3. Circuit 5-EC9 (BU) open (HS-CAN -)
4. Circuit 15-CF6 (GN/YE) open
5. Circuit 31-CF6 (BK) open
6. Circuit 31-CF13 (BK) open (with traction control)
7. ABS module

The instrument cluster (IC) communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits 4-EC7 (GY/RD) (HS-CAN +) and 5-EC7 (BU/RD) (HS-CAN -) provide the network connection to the IC. The IC shares the HS-CAN with the PCM, the restraints control module (RCM), the occupant classification system module (OCSM), and the ABS module. Voltage and ground for the IC is provided by redundant circuits. Voltage is supplied by circuits 15-GG14 (GN/RD), 29-GG14 (OG) and 75-GG14 (YE/BU). Ground is supplied by circuit 91-GG14 (BK/OG).

Possible Causes

1. Fuse
2. Circuit 4-EC7 (GY/RD) open (HS-CAN +)
3. Circuit 5-EC7 (BU/RD) open (HS-CAN -)
4. Circuit 15-GG14 (GN/RD) open
5. Circuit 29-GG14 (OG) open
6. Circuit 75-GG14 (YE/BU) open
7. Circuit 91-GG14 (BK/OG) open
8. IC

The scan tool communicates with the International Standards Organization (ISO) 9141 network through the data link connector (DLC). The generic electronic module (GEM) communicates with the scan tool through the ISO 9141 communications network, circuit 70 (LB/WH).

Possible Causes

1. Circuit 8-EE9 (WH/GN) open, short to ground or voltage
2. DLC
3. GEM

The scan tool is connected to the data link connector (DLC) to communicate with the high speed controller area network (HS-CAN) and International Standards Organization (ISO) 9141 communications networks.

Possible Causes

1. Fuse
2. Circuit 29-RA1 (OG) open
3. Circuit 31-RA1 (BK) open
4. Circuit 91-RA1 (BK/OG) open
5. DLC
6. Scan tool

Scheme 2

1. G1 CHECK THE DLC PINS FOR DAMAGE NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough inspection and verification before proceeding with the Pinpoint Test. Disconnect the scan tool cable from the DLC. Inspect DLC pins 4, 5 and 16 for damage. Are DLC pins 4, 5 and 16 OK? YES : Go to G2 . NO : REPAIR the DLC as necessary. CLEAR the DTCs. REPEAT the network test with the scan tool.
2. G2 CHECK THE VOLTAGE TO THE DLC Measure the voltage between the DLC C251-16, circuit 29-RA1 (OG), harness side and ground. Is the voltage greater than 10 volts? YES : Go to G3 . NO : VERIFY the central junction box (CJB) fuse 48 (10A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
3. G3 CHECK THE DLC GROUND CIRCUITS Measure the resistance between the DLC C251-4, circuit 31-RA1 (BK), harness side and ground; and between the DLC C251-5, circuit 91-RA1 (BK/OG), harness side and ground. Are the resistances less than 5 ohms? YES : REPAIR the scan tool. REPEAT the network test with the scan tool. NO : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.

See also:
• SUPPLEMENTAL RESTRAINT SYSTEM