I suspect that it is not really a pressure sensor and guage, but rather a oil pressure switch. If the pressure falls below (something like 5 psi) the switch triggers and shows low pressure. Also some vehicles PCM will read the switch, and will cut power to the fuel injectors, if it reads no pressue. I do not know if your engine falls into that category.
You may want to check the quality of the connection to the sensor, and if that looks good, consider replacing the sensor.
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BroncoJoe19
2006 Alt Fuel Jeep (electric)
'98 windstar 3.8L
'99 Crown Vic 4.6L
'90 Full Size Bronco 5.0L
I'm not a professional mechanic, take my suggestions with a grain of salt, or a cup of coffee 
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