Oil pressure light came on randomly - twice. Then never again..?

If it is just a warning light then it's a switch with 2 possibilities, just on/off. If you have a gauge that shows actual oil pressure then it would be a sensor which would vary its electrical resistance based on pressure. I think of a sending unit as referring to a sensor or even something more complicated like the float in the gas tank. A mechanic might call it a sensor when talking to a customer since the customer might not care about the details of how it works. And a sending unit works in a pair with a gauge or light. A sending unit and a receiving unit.

 

The sending unit provides the ground to light the light. Like Dr.Z mentioned... if there isn't enough oil draining back into the pan* for the oil pump to pump then the light will come on. If there is too much oil in the pan and the crank is hitting it the oil will foam up and oil pumps pump liquid, not air/foam.
behind the passenger side kick panel there is a large connector. This connects the engine harness to the dash harness. The yellow with blue tracer wire is the wire to the oil switch. if there is a rub through anywhere along this wire it will ground it and the light will come on.

*the newer Tacomas are having an issue with EXACTLY this problem. The oil drain holes are too small and/or are improperly placed so that when you are climbing an extreme angle hill the valve covers fill with oil and not enough is getting back to the pan... motors are being lost because of this oversight, Toyota is warrantying some motors and others they are not.

 

*update* I had my mechanic change the oil & filter and asked him to run a pressure test. He said it was "about 4" when it was at idle and "almost seemed to drop when it was revved up". He said he didn't have a gauge that would go low enough to tell me what the pressure dropped to. He tried to find another gauge and said he would have to make one... I have no idea what he meant.

It has been almost 2 weeks and no oil light. The truck seems to be OK but I noticed today that there is a little oil around where the filter attaches, and it seems fresh. I wiped it off and will check it again later on today.

No odd ticking or anything... I want to be proactive since I LOVE my truck and depend on it during the winter.

@Glamisman That's nuts about the new ones with motor issued because of the small drain holes!

Thank you all for your input!

 

See if you can hand tighten the oil filter a little more to be sure it's on tight. It would be a catastrophe if it loosened and you lost all the oil while driving.

 

Good call!