I recently purchased a used '08 Yukon XL SLT 4wd. This thing runs like it's brand new. Let me start with some of the issues though. About a week after buying it, the oil gauge started dropping off showing low/no oil pressure when idling at lights. A warning would come on saying 'low oil pressure, turn engine off' of something similar. I checked the oil, good to go, engine sounded fine, no codes were thrown, no check engine light, nothing. It would do it randomly when in idle but only when in gear, not neutral. I pulled the intake, changed the oil sender with another AC Delco part from Scoggin Dickey. It didn't change the issue. Remembering that the dealer said he had the oil changed while he had it cleaned up, I thought I would check under the truck and see what filter may be on it. Then pan and filter were covered in what looked like several years of oil. I scraped the filter off, it was a Ford Motorcraft filter. Referencing the part number, the oil filter should fit LS motors. Anyone else had an issue using a Ford Motorcraft filter on an LS motor? I had the GMC dealer change the oil & filter and all the low oil pressure warnings went away. I also cleaned all of the oil off the pan to try and find an oil leak. The oil wasn't low, and didn't appear to be very old. But the filter had tons of oil on it.

 

How many miles on it?

 

A little under 150,000

 

All is well now?

 

The low oil pressure warnings went away and oil pressure gauge has shown normal oil pressure since the filter and oil were changed. I haven't driven it enough yet to make sure there is no oil leak. My speculation is that the oil is leaking out of the front main seal or oil pan gasket.

 

So far everything is fine as far as the oil/oil pressure now. After a few weeks of owning the Yukon, it died and we had to jump start it. A couple days later it died again. So I replaced the battery. The next day the new battery was dead so I got a new alternator. I have been through two more alternators since the first one I replaced. It has now gotten to the point of it dying daily now. When driving it, I make sure it gets to 14 volts on the gauge cluster. I have checked for a draw on the battery and haven't been able to find anything.

I did notice that when the key is off, I can hear a relay or switch clicking at the driver door as if someone his hitting the lock button on the key fob. It happens every 2 minutes like it's on a timer. Maybe this is why I didn't see the draw on the battery.

The driver door mirror still power folds but the red blinker and power adjust stopped working.

When I put the transfer case into 4hi or 4lo there is a pop. It seems like it happens every time the front wheels make a full rotation. It feels like it's trying to engage in 4wd but isn't engaging.

So there's a few things I have to figure out on this thing still.

 

Looks like you have it scoped out! Hope you can get the various issues sorted out. Electrical can be such a PITA!

 

Yes Sir! Especially with all of the different modules and routing of all the stuff that come on newer vehicles.