oil pressure gauge query

[ashtheflash]

Hi,
Last week, and for about 5 days, my 4Runners, oil gauge was showing less than normal pressure, even on high speed. But no change in performance or overheating. Anyway, today, the gauge went back to normal reading, but shows, now and then low pressure, then returns to normal.
How can I verify if the problem is with the gauge, sensor, or, oil pump???

 

[fourwd1]

If you use GOOGLE you can find a Factory Service Manual online for a truck/4Runner near whatever year your's is.
The FSM has troubleshooting instructions for all of the above.

 

[Steve8v92]

And what you are basically going to have to do is find out where the Oil pressure sensor is located on the engine, remove it, get the right size fitting that will go into the block attach a line and guage to verify your oil pressure is good.