Yukon stability control

C0040 - Right Front Wheel Speed Circuit Malfunction
C0550 - ECU Malfunction - internal write / checksum malfunction
C0455 - Either:

• A bent terminal or poor connection at the SWPS may be one possible cause; or
• The vehicle stability enhancement system (VSES) electronic brake control module (EBCM) calibration may be the other possible cause.

C0296 - Transfer Case Delivered Torque for Stability Control System Circuit
http://www.obd-codes.com/trouble_codes/obd-ii-c-chassis-codes.php

If Autozone didn't get a code, then it's storing a B, U, or "C" code. Their code readers only read "P" codes.

GM has issued at least 3 service bulletins on this issue, ranging from a chaffed wiring harness to wheel speed sensor issues. Find all the ABS and Service Traction articles here
Yukon Archives Ricks Free Auto Repair Advice

check the resister next to the blower motor they burn out

I had the same problem in my Yukon Denali And after 4 throttle body's, replacing gas pedal, rewiring the grounds replacing sensors, took it to not one but two GMC dealerships who were useless they can't fix their own trucks they're not the brightest !!!! After thousands of dollars I found a mechanic very familiar with this issue you want the solution it will cost ya 500$ for me to tell ya!! Just kidding I know how frustrating this problem is okay here is the fix the problem is these electric throttle bodies are GARBAGE!!!!!!! Don't matter what u do or what u replace it will come back on unless u convert your electric throttle body to the old cable throttle the actual fix was 900$ but I spent thousands and thousands trying to fix it!!! Please save your money and tell ur mechanic u want to convert to the old cable throttle!!! Gmc is well aware of the problem but won't fix it for u cuz they're useless

Could be that the switch itself is shorting and allowing power to flow,if you can get to the switch I would use a voltmeter and see if there is voltage on the output side with the switch off.

your car is possesed treat it good it will treat you good. dont worry the only time my car will start is when a chick turns the key my car is a **** lol.

It is likely both your track bar and the lack of a steering gear box stabilizer. The bushings on your stock track bar can be replaced with polyeurethane or metal bushings which will help curb the problem.
The steering stabilizer attaches to your steering gear box and your frame allowing the steering to be more stable. I have put both on my truck and it drives like a caddy now as a result. If I had to choose between the two items, my money would go to the steering stabilizer first. I believe I bought mine here:
http://www.xtremediesel.com/bd-powerperformancedodgesteeringstabilizer.aspx
Hope this helps

vibration would have loosened the solder joint on one of the main two leads into the ABS pump on the ABS module.checkout and replace the defective solder, the stability control will work again.

if it has a 4.3 liter motor a 86 to a 97 if it has a 350 motor a 81 to a 96 will work hope this helps