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Home >> Ford >> 2002 >> Taurus SES, 3.0 S >> Repair and Diagnosis >> External Pages >> Different car >> Section 435 (Module Communications Network System -- Excursion & F250-F550 Super Duty) >> Diagnosis And Testing >> Communications Network >> Principles of Operation

Principles of Operation

WARNING: This page is about a different car, the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, 2003 Ford Excursion, and 2003 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The vehicle has three module communication networks:

The diagnostic tool connects to all three networks through the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one smart tester to be able to diagnose and control any module on the three networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The ISO 9141 communications network does not permit intermodule communication. When the diagnostic tool communicates to modules on the ISO 9141 communication network, the diagnostic tool must request all information or initiate module commands.

The ISO 9141 communications network will not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the ISO 9141 communications network loses power or shorts internally, communications to that module will fail.

The SCP communications network will remain operational even with the severing of one of the bus wires. Communications will also continue if one of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.

The UBP communications network will not function if the wire is shorted to ground or voltage. The UBP is different from the ISO communication network in that it allows intermodule communication.

The four-wheel anti-lock brake system (4WABS) module is on the ISO 9141 communication network. The module controls brake pressure to the wheels to keep the vehicle under control while braking. Refer to ANTI-LOCK CONTROL - 4-WHEEL .

The 4-wheel drive (4WD) control module (if equipped) is on the ISO 9141 communication network. The 4WD control module controls the four wheel drive functions for the vehicle. Refer to FOUR WHEEL DRIVE SYSTEMS .

The restraint control module (RCM) control the deployment of the air bags based on sensor input. The RCM is on the ISO 9141 network. Refer to AIR BAG RESTRAINT SYSTEMS .

The overhead trip computer (OTC) is connected to the ISO 9141 communication network. The OTC computes and displays in metric or English: average fuel economy, distance to empty, and compass heading. Refer to INFORMATION AND MESSAGE CENTER .

The parking aid module is connected to the ISO 9141 communication network. The module controls the sensors in the rear bumper that detect close objects when the vehicle is in reverse. Refer to PARKING AID .

The powertrain control module (PCM) is on the SCP communication network. The PCM controls the engine for better fuel economy, emissions control, and failure mode detection and storage. For gas engine, refer to SYSTEM & COMPONENT TESTING - GASOLINE . For diesel engine, refer to SYSTEM & COMPONENT TESTING - 7.3L DIESEL or SYSTEM & COMPONENT TESTING - 6.0L DIESEL for diagnosis and testing of the PCM.

The auxiliary powertrain control module (APCM) is on diesel engine equipped vehicles. The APCM is connected to the SCP communication network. The APCM provides an operator interface to the drive-by-wire powertrain control system to affect charge protection, rpm control, and manual throttle control between 1,300 and 2,500 rpm.

The passive anti-theft system (PATS) module (Excursion) is connected on the SCP communication network. The PATS module enables or disables the PCM to deter drive-away theft. Refer to ANTI-THEFT - PATS .

The instrument cluster is connected to the SCP communication network and the UBP communication network. The instrument cluster displays driver information, including tachometer reading, fuel level, engine coolant level and speed. The message center is included in the high option level cluster and displays door/hatch ajar information, lamp outage and low washer fluid level. Refer to INSTRUMENT CLUSTER .

The driver seat (DSM) module (if equipped) is connected to the UBP communication network. The DSM controls the driver power seat. In addition, the DSM is programmable to store seat position and pedal position. Refer to SEATING .

The air suspension control module (if equipped) is connected to the UBP communication network. The air suspension control module controls the rear ride height on F350, 450, and 550.

The electronic automatic temperature control (EATC) module (Excursion) is connected to the UBP communication network. The EATC module controls automatic climate functions that maintain the vehicle at a constant temperature setting. Refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION .

The vehicle security module is on the UBP communication network. The vehicle security module controls a variety of systems:

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