Module Communications Network System: Overview Ford Escape I

Principles of Operation

The vehicle has two module communications networks. The standard corporate protocol (SCP) network, which is an unshielded twisted pair cable (data bus plus, circuit 914 [TN/OG] and data bus minus, circuit 915 [PK/LB]); and the international standards organization (ISO) 9141 network which is a single wire (circuit 70 [LB/WH]). The diagnostic tool can connect to both 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 two networks from one connector. The DLC can be found under the instrument panel on the driver side.

The SCP communication 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 ISO 9141 communication network does not permit inter-module communication. When the diagnostic tool communicates to modules on the ISO 9141 communication network, the diagnostic tool must ask for all information; the modules cannot initiate communications.

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

There are two modules linked to the SCP communication network and three modules linked to the ISO 9141 communication network.

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.

The passive anti-theft system (PATS) is integrated into the PCM module. The PCM/PATS system is connected to the vehicle electrical system, the transceiver module, the vehicle SCP communications network and the vehicle anti-theft indicator located in the instrument cluster (IC). The PCM module uses a microprocessor to control the system functions as well as illumination of the anti-theft indicator. The illumination command is sent from the PCM through the SCP communications network to the IC, which in turn sends power to the anti-theft indicator. The PCM module microprocessor stores the ignition key codes in non-volatile memory. The PCM and IC modules can be diagnosed through the data link connector.

The restraint control module (RCM) is on the ISO 9141 communication network. The RCM controls the deployment of the air bags based on sensor input.

The generic electronic module (GEM) is on the ISO 9141 communication network. The GEM controls a variety of systems

1. rear wiper
2. cargo lamps
3. interior lamps
4. exterior lamps
5. accessory delay
6. perimeter anti-theft (if equipped)

The anti-lock brake system (ABS) control module is on the ISO 9141 communication network. The ABS module controls the brake pressure to the four wheels to keep the vehicle under control while braking.

Scheme 2

1. Verify the customer concern.
2. Visually inspect for obvious signs of electrical damage.
3. If the concern remains after the inspection, connect the diagnostic tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle: check that the program card is correctly installed. check the connections to the vehicle. check the ignition switch position is in RUN. If the diagnostic tool still does not communicate with the vehicle, go to «PINPOINT TEST H»(ref-177213-S01822507442005052500000) .
4. Go to «PINPOINT TEST PC: DATA LINK DIAGNOSTICS NETWORK TEST»(ref-177213-S11953477042005052500000) .

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1. Disconnect the battery ground cable.
2. Strip the wires.
3. Solder the wires. Install the heat shrink tube. Twist the wires together. Solder the wires together.
4. Bend the wires back in a straight line.
5. Position the (A) heat shrink tube over the (B) wire repair. Overlap the heat shrink tube on both wires.
6. Use the heat gun to heat the repaired area until adhesive flows out both ends of the heat shrink tube.
7. Reconnect the battery ground cable.