Mrs. Cusser's 2005 GMC Yukon Denali with 6.0 engine, almost 200K miles. She says that for a month or so that on first startup of the day that there's a message stating "oil pressure low" that appears, but the oil pressure is normal. So she switches the engine off, and starts it again, and the message does not re-appear (until first startup the next day). The oil level is fine, I've used 5W-30 full synthetic for the 8 years we've had it as did the previous owner. There are no other engine issues or noises. Morning low temperatures are about 45F here. Any ideas??? Thanks.

 

Someone from GM online saw this problem posted, contacted me. When I responded, she asked if I had taken it to a dealer. For an intermittent - are you kidding !!! I referred her to GM Sunroof-Denali complaint #71-1172386297, my only experience with a GM dealer, about the Yukon's inoperative sunroof 5 years ago 2005 Yukon Denali Sunroof - I am so pi$$ed !!! - Automotive Forums .com Car Chat where the dealership literally threw up their hands and actually said "we have no idea what the problem is", then fought about refunding my money, even though they took my money after assuring that it would be a FIX, and not a guess.

So over my dead body will I ever visit a GM dealership again !!!

 

I'm reporting that I have changed the oil on this 2 weeks ago (stayed 5W-30 synthetic, Mobil) and upgraded to a Wix oil filter, and the oil pressure low warning has not re-appeared, even though it has been below 40 °F overnight. 200K miles on this. So - so far, so good !!!

I have not changed to a thicker oil, still using what owner's manual states, 200K miles on this.

 

OK, was able to locate the oil pressure sending unit rear center of engine, pretty buried. And was able to remove the harness without breaking it.

Bad news looks like a real hassle to R&R the sending unit and the filter below it. So if need be, that will be a job for local independent mechanic.
https://www.oreillyauto.com/detail/b...2FSwitch&pos=1

https://images.oreillyauto.com/parts...26-040-007.jpg

 

I also have a low oil pressure warning but I got it to kinda go away. 3k mile oil changes with full Synthetic oil and a good filter had kept my low oil issues at bay. 40k miles later no issues. I'm just gonna replace the O ring in the oil pump at some point. (That's really where the issue is)

But not every one of these trucks has a filter there. I think the newer ones dont, and your being a 2005 means no. (If I remember correctly) my 2004 sure doesnt have one as I checked. But my .motor was replaced 45k miles ago so who knows.

On my 2004 I could NOT find the filter there. Replaced my oil pressure sending unit too. You dont need to remove the intake manifold either.

 

June 2021: 236K miles, sold this Yukon Denali 6.0 liter. Never had any issues with oil pressure/engine failure other than the warning.

And purchased a 2011 Yukon XL Denali 6.2 liter with 73K miles, very similar engine-wise.