Trailblazer oil pressure gauge doesn't tell you the oil pressure (4.2L engines) Video 1

Unplug the oil pressure switch in your 4.2L Trailblazer/Envoy/etc and you'll find that the oil pressure gauge still shows you oil pressure. How is this possible? Where is this oil pressure reading coming from if the switch is unplugged? To find the answer, we're going to have to dig through the FSM and test the oil pressure ourselves. Only that isn't going to be as fast and easy as it may seem.
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