PCI Bus System

The Programmable Communication Interface (PCI bus) multiplex system consists of a single wire. The diagnostic junction port acts as a splice to connect each module and DLC. Diagnostic junction port is located below instrument panel to left of steering column. Each module uses its local ground as bus reference. If more than one module is trying to access the PCI bus at one time, the code being sent determines which message has higher priority, and is then allowed to access bus first. Communication over the bus is essential to proper operation of vehicles on-board diagnostic systems and Diagnostic Readout Box (DRB-III(R)). Problems with operation of bus or DRB-III(R) must be corrected before proceeding with diagnostic testing.