Principles of Operation: Notes

WARNING: This page is about a different car, the 2004 Ford RV Cutaway, 2004 Ford Econoline, 2004 Ford E450 Super Duty, and 2004 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

The vehicle has 3 module communication network protocols:

Standard corporate protocol (SCP) communication network
International standards organization (ISO) 9141
Controller area network (CAN) (diesel only)

The SCP is an unshielded twisted pair cable, data bus plus, circuit 915 (PK/LB) and data bus minus circuit 914 (TN/OG). The ISO 9141 communications network is a single wire network circuit 70 (LB/WH). The CAN is an unshielded twisted pair cable, data bus, circuit 3022 (PK/YE) and circuit 3073 (RD/WH). All networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one diagnostic tool to be able to diagnose and control any module on the networks from one connector. The DLC can be found under the instrument panel and the steering column.

The SCP and CAN 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 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 ask for all information; the modules cannot initiate communications. 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.