This 2006 Nissan Pathfinder SE (145,143 mi.) with a 4.0 and RWD came into the shop with a customer complaint that the oil pressure gauge had, over the course of a day or so, pegged out on "H" (i.e. High) and would not move or fluctuate.
First things first, we confirmed the level and condition of the oil and filter. Everything was good there. Next we confirmed the complaint. As soon as the vehicle was started, the oil pressure gauge hand went straight to the "H" and did not move. See the picture below:
The quickest check for this problem is to go underneath the vehicle and unplug the oil pressure sensor/switch. It is located on the right side (i.e. passenger side) of the engine, toward the front on the oil pan. We unplugged the sensor and then restarted the vehicle to see what would happen. Below is a picture of the sensor unplugged.
When we did this the oil pressure gauge stayed at "L" (i.e. "Low") and did not move at all. The red oil warning light also illuminated, as it should. Below is a picture of the dash with the vehicle running and the sensor unplugged.
With the sensor unplugged and the vehicle running, the gauge should bottom out at (or below) the "L". This proves that the circuitry is good and the dash is not the issue. With this response, it was obvious the sensor itself was the culprit.
We replaced the oil pressure sensor, reconnected the pigtail and started the vehicle. Now, the gauge read properly, showing good oil pressure.
This repaired the customer's issue and another one was out the door.
