Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Programmable Communication Interface Bus Circuit
The Programmable Communication Interface (PCI) bus circuit is a multiplexed network capable of supporting binary encoded messages shared between multiple modules and the Data Link Connector (DLC). The PCI bus circuit is connected by a single Violet/Yellow wire. Each PCI bus circuit component uses its local grounds as bus reference. If more than one module is trying to access the PCI bus circuit at one time, the code being sent determines which message has higher priority, and is then allowed to access bus circuit first. Communication over the bus circuit is essential to proper operation of vehicles on-board diagnostic systems and Diagnostic Readout Box (DRBIII) scan tool or generic scan tool. Problems with operation of bus circuit or scan tool must be corrected before proceeding with diagnostic testing.
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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