Differential service on 2003 denali

rough guess is that there is a connection that is not properly connected

I'll try to help, everytime something gets replaced on these yukons, that circuit needs to be RESET ! Is there a reset button, on your steering wheel, to reset a variety of functions ? , check owners manual, or call your dealer for better advise

my car is denaly xl 2003 ,I stoped it with good condetion but when I came and try to start I foun not working I not remot not open the doors also I noticed not remember my infomation.I need your support to rectify this problem.

There are some vehicles that require a special oil. Usually 80 w 90 wieght oil is used in Differentials. I recommend that you drain it first then add oil. Because oil and synthetic oil do not mix. You can call a dealer service department and they can tell you for sure.

This code is saying that your catalytic converter is no longer doing it's job. You would need to replace the catalytic converter to get this light to go out.
A new converter assembly from a GMC dealer is around $500, and the labor is 1.4 hours to replace it, plus miscellaneous gaskets and/or clamps. If the labor at your dealer is $100/hour, you're looking at about $650-700 for this repair. You may be able to get it done cheaper with aftermarket parts at an independent shop. I would suggest that you call around and get quotes before bringing it in.

Not really, but you do need a floor jack and good jack stands. Air tools help because most bolts will be tight and stuck.

all depends on what shop you go to. Have you had the fluid changed in it? They also have special lube you can put in to differential's to help the shimmy, noises, and all that go away.

I have experienced whining differentials that lasted many years. Check that oil level though, but usually whining comes from bearings and/or bad alignment with the ring gear and pinion.

Look in the glove box and look at the GM PRO Code sticker. Look for the codes GU1=axle ratio 2.41 GU2=ratio 2.73 ect up to GU6=ratio 3.42 or it may be GV which is the rear axle ratio codes. As long as the codes on the Tahoe matched the Denali your good to go. Good luck and keep me posted, If you'll like me to let you know your rear axle ratio and if it's a locking or not just ask, be glad to help

my service ride control was on took to dealer said exhaust valve was bad new compressor was installed prts n lbr 875.00