F 250 2WD Super Duty V10-6.8L VIN S (1999)
Multiplex Communication Network: Description and Operation
Motorhome
The vehicle has two module communication networks: the Standard Corporate Protocol (SCP), which is an unshielded twisted pair cable (data bus plus,
circuit 914 [T/O] and data bus minus, circuit 915 [PK/LB]); and the International Standards Organization (ISO) 9141 communications network which is
a single wire network (circuit 70 [LB/W]). Both networks can be connected to New Generation STAR (NGS) Tester by one connector called the Data
Link Connector (DLC). This makes troubleshooting 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 near the steering column.
The ISO 9141 communication network does not permit inter-module communication. When NGS Tester communicates to modules on the ISO 9141
communication network, NGS Tester must ask for all information; the modules cannot initiate communications.
The Standard Corporate Protocol (SCP) 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 battery positive voltage (B+), or if a termination resistor, but not all, are lost.
Unlike the SCP network, the ISO 9141 communication network will not function if the wire is shorted to ground or battery positive voltage (B+). Also, if
one of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module or all modules will fail.
The 4-wheel anti-lock brake control module is connected to the ISO 9141 communication network. The module controls the brake pressure to the four
wheels to keep the vehicle under control while braking.
The Powertrain Control Module (PCM) is connected on the SCP communication network. The PCM controls the engine performance, electronic
ignition, emission controls and on board diagnostics.
