I have a 2004 Yukon XL 2500. And have a flat tire.

https://www.autozone.com/repairguides/Escalade-Suburban-Tahoe-Yukon-Denali-DenaliXL-YukonXL-1999-2005/Seats-2004/Driver-Seat-Schematics/_/P-0996b43f80370a19 https://www.autozone.com/repairguides/Escalade-Suburban-1500-2500-Tahoe-Yukon-Yukon-XL-1500-2500-2006-2007-Yukon-Denali-and-Yukon-Denali-XL-2005-2006/Power-Seats-2007/Driver-Seat-Schematics/_/P-0996b43f80cb1bbc https://www.tahoeyukonforum.com/threads/power-seat-wiring-help.63730

Have you looked under the pas seat. Or pull the floor up at the rear where the spare tire should be

this is a safety feature on all gm vehicles. tighten spare tire all the way up until you hear 2 clicks in the spare tire compartment and also you should feel it in the wrench then lower the tire and this should work if not then start the process over

I’m happy to help further over the phone at https://www.6ya.com/expert/john_5260ce46f2f674cc

you need a special key.the port beside the tag bracket.

You need to dig out the jack and tools .. The spare is held in place by a cable winch that needs to be cranked down.

Rotate the hoist shaft counterclockwise in order to lower the spare tire to the ground. Continue to rotate the shaft until the spare tire can be pulled out from under the vehicle and removed. If the spare tire does not lower to the ground, the secondary latch is engaged causing the tire not to lower.

If the secondary latch is engaged and the cable end is visible, perform the following procedure: 3.1. Tighten the cable by rotating the hoist shaft clockwise until you hear 2 clicks or feel it skip twice. You cannot overtighten the cable. 3.2. Loosen the cable by rotating the hoist shaft counterclockwise 3 or 4 turns. 3.3. If the spare tire can be lowered, repeat steps 1 and 2 to see if the spare tire can be removed. 3.4. If the spare tire cannot be lowered, rotate the hoist shaft counterclockwise until approximately 15 cm (6 in) of cable is exposed. 3.5. Raise and support the vehicle. 3.6. Place a transmission jack, or equivalent, under the spare tire. 3.7. Position the center of the transmission jack under the secondary latch release button at the center of the spare tire. Arrange the arms of the transmission jack so they will support the tire after it has been released. 3.8. Raise the jack until the spare tire stops moving upward and is firmly held in place, releasing the secondary latch. 3.9. Lower the tire. If the spare tire is hanging by the cable, rotate the hoist shaft counterclockwise until the tire is low enough to remove.

check your spare tire for proper inflation its tripped me up before

you need a tool that goes in a slot in the rear bunper

Code po449 is the canister vent valve solenoid error.This is a common problem with these valves because they are under the truck in the rear by the spare tire and they get all the dirt and water and snow,if you live in an area where you get snow.You will find it on the canister under the vehicle by the spare tire.

Check this site for info- there are 16 different 'keys', so it would probably be best to follow instructions on how to use a 'bolt extractor' to drop the spare tire, and remove the 'key ' insert, so you can lower it w/ a 3/8 drive socket extension in the future, and lock it with a cable lock for security.
http://www.ford-trucks.com/forums/831281-lost-ford-spare-tire-key-this-works-great.html