"System voltage" refers to the electrical potential or energy in an electrical system. It refers to the level or amount of voltage that exists within a particular system or network to power electrical devices and equipment. Full definition
The current gauges offer up oil pressure, oil temperature, electrical system voltage, and transmission temperature. (automobilemag.com)
If checking the charging system voltage isn't working, there should be another circuit that you could use. (mechanics.stackexchange.com)
If I'm using a spark tester with an adjustable gap set to the correct gap for my car's ignition system voltage, what should the spark look like? (mechanics.stackexchange.com)