I have an 04 Rainier with the 5.3L V8, just rolled over 100k miles.

Just started having a very quick low oil pressure alarm and seems to be running a little lower then normal as well. Idle and low load (1500 rpm) will read around 30 or so (use to be right around 40) and occasionally it will skip down to 20ish (alarm message on dash) and go right back up.

I had a low reading on my 05 Bonneville SLE (3800 V6) and replaced the oil pressure switch to correct it.

Does this sound like a probable cause on the Rainier? Where is the oil pressure switch located at on the Rainier and how easy to change / fix?

Thanks!

I would start with testing the pressure with a mechanical tester. The electronic ones are not very reliable.

Thanks for the info. I do not have a mechanical gauge to hook up and is why I was asking how easy changing out that pressure switch was, is only like a $40 part.

Never done one on that engine. But it should be no more then pull the sensor and put in the new one. Should be right by the oil filter.

the sensor is on the top of the block at the back by the fire wall screws in like a knock sensor

heres the diagram its part number 706

Thanks for the info and the diagram!

From what I am explaining think it is at least a decent chance it is this part?

It might be the oil. When the oil gets old, even at 2000 miles, it loses the abiliy to build pressure. When old oil gets hot, the pressure drops even more.

How long has it been since an oil change?

Oil change was just over 3000 miles ago, is due to be done.

Change your oil first,(considering its due) and watch your pressure gauge again. If it returns back to normal, your fine. It was just the oil being old.