This is from alldata for a 93 4.0 sending unit. I cant find anything converting the readings to psi.
The oil pressure indicating system consists of an instrument voltage regulator, electrical oil pressure gauge and a sending unit which are connected in series. The sending unit consists of a diaphragm, contact and a variable resistor. As oil pressure increases or decreases, the diaphragm actuates the contact on the variable resistor, in turn controlling current flow to the gauge. When oil pressure is low, the resistance of the variable resistor is high, restricting current flow to the gauge, in turn indicating low oil pressure. As oil pressure increases, the resistance of the variable resistor is lowered, increasing current flow to the gauge, resulting in an increased gauge reading.
This is from a 2000 4.0 oil pressure sensor.
The 3-wire, solid-state engine oil pressure sensor (sending unit) is located in an engine oil pressure gallery.
The oil pressure sensor uses three circuits. They are:
- A 5-volt power supply from the Powertrain Control Module (PCM)
- A sensor ground through the PCM's sensor return
- A signal to the PCM relating to engine oil pressure
The oil pressure sensor has a 3-wire electrical function very much like the Manifold Absolute Pressure
(MAP) sensor. Meaning different pressures relate to different output voltages.
A
5-volt supply is sent to the sensor from the PCM to power up the sensor. The sensor returns a voltage signal back to the PCM relating to engine oil pressure. This signal is then transferred (bussed) to the instrument panel on either a CCD or PCI bus circuit (depending on vehicle line) to operate the oil pressure gauge and the check gauges lamp. Ground for the sensor is provided by the PCM through a low-noise sensor return.
