2005 Yukon Message stating "oil pressure low"

OK, new question, and I know you folks all want Mrs. Cusser to be happy...

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 light goes out as normal, and the oil pressure is also 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.

The right thing to do here is to actually check the oil pressure with a gage when first started, if ok the bcm is getting or giving false info. Then the next step is a possible bad sender, so your dash gage shows numerical good pressure, but a warning lite comes on?

The right thing to do here is to actually check the oil pressure with a gage when first started, if ok the bcm is getting or giving false info. Then the next step is a possible bad sender, so your dash gage shows numerical good pressure, but a warning lite comes on?

Thanks for the response.

Mrs. Cusser drives this, I took a look. The oil pressure gauge works fine, takes like 2 seconds after first start up to get to proper pressure and remains GOOD, so I think that the sender itself and oil pressure itself are fine (engine has not self-destructed). If the oil sender was easier to access, I'd think about just swapping in a new one.

There is no "oil light", original post has that mistake; there is the gauge and the information center (DIC) actually has stated "oil pressure low" at first start up of the morning, and seems to be doing that more lately.

I'm due for oil change on that anyway, already bought the 5W-30 synthetic oil and a Wix filter, think possibly that the drainback valve in the existing oil filter isn't closing fully, causing a momentary "oil pressure low" message that does not come on if she shuts off the engine and then re-starts it.

I wonder if at 200K miles that a higher-viscosity oil would be warranted.....

Hopefully that may help, GM did have some oil pump issues on that engine. The drain back issue only applies to horizontally mounted filters.

Hopefully that may help, GM did have some oil pump issues on that engine. The drain back issue only applies to horizontally mounted filters.

On that engine the oil filter is vertical.

So no possible way drain back issues.

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 http://www.automotiveforums.com/vbulletin/showthread.php?t=1086523 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 did an oil change (Mobil synthetic) and new Wix filter about 3 weeks ago, and the message has not reappeared.

Unfortunately the manufacturer has little control over the service dept operating policies, so small claims has been commonly used to resolve such issues, in NYS it is labeled ineffective repairs. Glad its resolved.

Aug. 31, 2019 update. The Yukon is still running fine. Mrs. Cusser states that the warning occasionally shows up on start up on cooler mornings.

I've driven it about 2 miles personally since then.

Two months ago the mechanic replaced the blower fan and blower resistor to fix the AC fan operation. He wasn't concerned about the oil pressure low warning, and said not worth it to replace the oil pressure sending unit.

Another item which might affect your diagnosis is that the oil pressure instrument on the dash may not actually be a gauge, but an indicator. Some models, like B-body cars and K-body MPVs use an oil pressure "sender" which is actually just a switch. The I/P uses a resistor to position the oil pressure "gauge" at a predetermined point of sweep just to indicate that sufficient oil pressure is present, and doesn't actually vary to indicate relative oil pressure.

If your oil pressure instrument doesn't vary from dead cold startup to full-hot idle pressure, it may be one of this type. This is why a mechanical gauge tapped into the system is important for diagnosis.

Also, read your owners manual carefully. There is usually a sliding scale for determining the appropriate oil viscosity under various temperature ranges. Despite the oil filler cap displaying the "5W-30" script it is often appropriate to use 10W30 in temperatures above 25°F - Right in the owners manual.

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.