The dual ground configuration is very common but now that batteries are mounted in out-of-the-way places outside of the engine department a single battery ground cable is used to ground the battery negative terminal to the engine block.
In tracing electron current, we find an unusual way that generator electron current flows when the engine is running if the battery negative terminal is grounded to the engine block and to sheet metal at the same time.
During NACE Automechanika 2017 Eric Ziegler in his class, “Essential Diagnostics - The Steps You Need To Take In Tackling Every Drivability and Electrical Concern,” outlined his thoughts on what makes a good diagnostic process – a process that can be applied to any troubleshooting challenge you face.
So what to do about HMI? There are a lot of service opportunities that can be addressed because the radio in a vehicle isn’t operating correctly. Unless these vehicles are still under the factory warranty then there are plenty of service options available.
Modern vehicle systems are based on electronic controls over mechanical systems. To diagnose failures within these systems, we must first separate these systems from one another by analyzing the electronic control system. We need to look at a vehicle’s circuits for voltage change over time. This will be accomplished with an oscilloscope.
Having an understanding of how the network is laid out and the protocol or protocols it communicates with are essential. A wiring diagram and a quick read of service information will usually provide a quick insight of the network’s layout and communication characteristics.
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