Passenger door does work automatically anymore

Usually damaged wires in the wiring harness where is goes from the door to the door frame. The drivers side always fails well before the passenger side do to all the use it gets.

https://www.google.com/search?q=2004+Yukon+Denali.+driver+side+automatic+door+lock+works+intermittently

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no all is related to one fuse you can remove the door internal controls and decore and remove center lock motor plug and test two connectors with multimeter with set on 12v and then lock un lock door and check the reading of the multimeter if it read signal then all plugs and wires from central lock control unit to the door central lock unit is okay it this cae you have to replace the door central lock unit with the same if no signal is readed while you lock unlock the door then you have to check central control unit and all wire plus out of it to the door plug

2- you can remove central control unit from driver door and test it in passenger door (usually the same unit ) if it works with lock unlock its then the replaced unit is faulty and needs to be replaced if it not work then check plugs wires from central lock unit (usually found inside driver door ) to the central lock unit in passenger door

3- check signal for said door fro the output of central door unit if no signal then it mean that faulty central lock control unit

Motor on seat belts faulty

Check the battery cables for clean and solid connection.

Before you ever disconnect any vehicle battery, you need
to have or know about anything that may have to reset.
Somethings you can do & some things need a professional scan
tool
I would say now is the time to gather the info & educate yourself,
as most vehicle are way more complex than a 2002
You really need factory service & diagnostic manuals, &
due to the fact almost no one works on their own cars anymore,
due to technology,that is expensive to buy,I have for 50 years
but that is my hobby & ongoing study
I would ask a tech at a dealership or use Google to search out
the question or solution to you current problem

Sounds like it., check and clean connections to button first.

When you start the car, the HVAC air control doors are automatically moved to a default position, and then as the engine heats up, the doors are moved to the requested position. Probably a problem with the passenger side electrical air mix door actuator, but could also be the passenger side temperature control. Try changing the setting to see if that has any effect.
You will need the service manual to locate the actuators, to check them and replace if necessary.

both the rear passenger side wont unlock ???? How many doors are on the passenger side ? Or both back doors don't unlock ? Two relays lock / unlock the back door's Not the lift gate . The BCM controls the relay's . The relay's are located in the rear fuse box . Under back seat .

Its time to stop being afraid of the unknown. there is no doubt that you will need to remove the inner door panel to access the electrical modules behind the buttons. https://www.youtube.com/watch?v=p2_f7NkjH8E hope this helps.