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AV-SCANNER / Service function guides / Battery and charging
This guide covers the complete process of diagnosing a Controller Area Network (CAN) bus fault, from understanding the physical and data-link layers through to isolating a module that is pulling the network down. It is written for working mechanics and experienced DIYers who already own a digital multimeter and a scan tool with live data capability. By the end you will be able to measure bus voltages and resistance, interpret CAN waveform patterns, and systematically disconnect modules to find the culprit without guesswork. The procedure applies to passenger cars and light commercial vehicles across most makes, with notes on the variations you will meet in practice.
Guidance is general and covers many makes. Exact procedures and values vary by model, so confirm them in the factory service information for your vehicle.
Download all 11 sections as a branded PDF to use in the workshop.
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