Yes you can but, I would advise adding the mechanical gauge to the system but leaving the original intact.
Remove oil sending unit and replace with a mechanical gauge
mechanical
"T" into the existing oil pressure gauge with brass pipe fittings. This way you will have the original oil pressure gauge and the mechanical oil pressure gauge. Don't forget to use thread sealer.
The gauge should be electrical.
The oil pressure gauge in a 1999 Ford Explorer is ELECTRIC
Pressure Indicator is any instrument that indicates pressure. Pressure Gauge is also a type of pressure Indicator. It is a mechanical device. Pressure indicators can work on mechanical deflection (in case of pressure gauge) or Piezo electric effect, change in capacitance, change in inductance etc. These are generally digital type instruments.
You will need to remove your oil pressure sending unit and install a mechanical gauge to get a true reading. You need to start out cold and write down the pressure reading and also once it warms up to operating temperature. If the pressure gauge is not the same as the mechanical one you have a bad pressure switch.
A Buick with a 3.8 liter engine does not have an oil pressure switch. There is an oil pressure gauge. The gauge can be accessed by removing the dashboard panel. Unhook the wiring harness to the gauge. Reverse the process to replace the gauge.
Remove oil sending unit and replace with a mechanical gauge to check actual engine oil pressure
Depending on mileage--could just be a sign of engine wear Remove oil sending unit and replace with mechanical gauge to determine actual pressure
replace oil sensor unit
Test with a mechanical gauge to accurately detemine oil pressure Could just be a defective oil pressure sensor