PCI Bus System

The Programmable Communication Interface (PCI) multiplex system (bus) consists of a single wire. The PCI bus wire is primarily Violet/Yellow with an extra tracer color to help distinguish between different connections. The BCM acts as a splice to connect each module and DLC. 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 (DRBIII(R)). Problems with operation of bus or DRBIII(R) must be corrected before proceeding with diagnostic testing.