Econoline E350 1 Ton V8-5.4L Prop SOHC VIN Z (1998)
Information Bus: Description and Operation
The vehicle has two module communication networks:
The Standard Corporate Protocol (SCP) network, which is an unshielded twisted pair of wires (data bus plus, circuit 914 and data bus minus, circuit
915), and the International Standards Organization (ISO) 9141 network which is a single wire (circuit 70 [/W]). Both networks can be connected to New
Generation STAR (NGS) Tester at one connector called the Data Link Connector (DLC). This makes troubleshooting these systems easier by allowing
one 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
directly below the steering column.
The ISO 9141 network does not permit inter-module communication. When NGS Tester communicates to modules on the ISO 9141 network, NGS
Tester must ask for all information; the modules cannot initiate communications.
The SCP 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 chassis ground or battery positive voltage (B+) or a termination resistor is lost. This faulted condition is detected and reported to the host by
the module's network bus interface circuits.
Unlike the SCP, the ISO 9141 network will not function if the wire is shorted to chassis ground or battery positive voltage (B+). Also, if one of the
modules on the ISO 9141 network loses power or shorts internally, communications to that module will fail. There are two modules on each network.
Module Configuration
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 air bag Electronic Crash Sensor (ECS) module is on the ISO 9141 network. The ECS controls the deployment of the air bags based on sensor
input.
The 4-Wheel Anti-lock Brake System (4WABS) is on the ISO 9141 network. The 4WABS controls the brake pressure to the four wheels to keep the
vehicle under control while braking.
