Oil Pressure Gauge: Description and Operation

With the ignition switch in the ON or START position, power is supplied
^ through 1O A fuse [No. (10), located in the fuse block (J/B)]
^ to combination meter terminal (29) for meter and gauges.
Ground is supplied
^ to combination meter terminal (13) for gauges and tachometer, and
^ to combination meter terminal (22) for speedometer
^ through body grounds (M3) and (M90).

The oil pressure gauge indicates the engine oil pressure. The reading on the gauge is based on the resistance of the oil pressure sending unit.
As the pressure of the engine oil in the oil gallery increases, the resistance of the oil pressure sending unit increases. A variable ground is supplied to terminal (32) of the combination meter for the oil pressure gauge.