Toyota FJ40 - Testing Oil Pressure Gauge

I tested the oil pressure gauge by grounding the sending wire. The needle went all the way to high so the gauge itself is working. I then removed the mechanical gauge the previous owner installed and installed a new oil pressure sending unit in it's place. Started the engine and the oil pressure gauge is now working as well! I assume the previous owner just liked mechanical gauges or the original sending unit failed and he just decided to install the mechanical unit instead of replace the sender. Either way I'm glad it's still working.