Where is the pcv valve on a 2004 yukon denali?

SOURCE: 02 yukon denali security light stays on will not

Several GM products, including the Chevrolet Impala and Malibu, the Oldsmobile Alero, the Pontiac Grand Prix, and Saturn Ion, have issues with the Security light coming on. This is many times an indication of a failing Body Control Module (BCM). Initially, the Security light will come on then go off, progressing to a constant on light, before the car will refuse to start. Other symptoms may include erratic action of electronics, a clicking sound coming from the glove box, and the air conditioning failing to blow cold air. I recommend a shop that specializes in the electronic systems of vehicles to diagnosis and make the necessary repairs. They should keep the car until they replicate the symptoms described. A new BCM from GM should cost about $230; plan on another $200 for them to diagnose the problem, replace the unit, and program the new unit. The dealers quote between $700 and $1,100 for the same repair. My experience and the experiences I have read on the internet, indicate the new BCM should last only about a year.

SOURCE: How do you change the transmission fluid in a 2004

At the bottom of your transmission there is a large square/rectangular pan (depends which trans you have). Have a large drain pan to catch 5 to 9 liters/quarts of transmission fluid. Undo all of the retainer bolts and carefully lower the pan (this can get messy for the unexperienced) .
In some cases the rear transmission mount may need to be undone and the rear of the trans lifted to allow clearance for the pan to be slid past the crossmember.
Replace the trans filter too!

SOURCE: 2004 denali check engine light stays on

There is no p01001, it's either p0100, or p0101.
Anyway, it's the mass air flow sensor that's bad. The p0171 and p0174 is a lean condition on bank 1 and bank 2, which are the oxygen sensors. Change the mass air flow sensor and that should take care of the p0171 and 74 codes.
The mass air flow sensor can cause the 02 sensors to read lean.
The u1301, is a class 2 circuit short to battery. That, you have to test wires to find with a voltmeter/continuity tester.
I would try and find that short before changing the flow sensor, you don't need the new one shorting out, they are not that cheap.