The diagram will show a chassis ground symbol (usually a line with three decreasing horizontal bars) labeled things like "E1," "E2," or "E3." Start here. Most electrical issues are poor grounds. The Pz071 will show you which ground connects to the cylinder head and which to the frame.
Need help with a specific PZ071 number? Reply with the full code (e.g., PZ071-32010) and your vehicle model/year for a targeted pinout. Toyota Pz071 Wiring Diagram
Follow the thick Red or White wires from the battery, through the main fuse (often a 60A or 80A fuse labeled "ALT" or "MAIN"), to the ignition switch, and finally to the Pz071 connector. Any break here kills the entire system. The diagram will show a chassis ground symbol