Spark Plug Job Fail?
 

Hey guys, I replaced my brothers spark plugs on his truck (2008 Avalanche) the other day and now his traction control light is on and he has a service stabilink message in the message center. I checked the gap before installation, hand threaded them in, tightened them down with a ratchet (I didn't have a torque wrench so I got them snug but not overly tight), plugged the wires back into the plugs and coil packs. In hindsight there are a couple mistakes I made 1. I didn't replace them one by one, I took all the wires out and laid them down sequentially and 2.When I unplugged the wires from the spark plugs it took a lot of stength getting the boot off so after I was done with everything I gave the boots a good tug to make sure none were loose and noticed a couple of them that weren't loose but they came off way easier than they went on so I didn't know if that was normal. ANY help is appreciated.

Sounds like you were careful overall, but I’d double-check the coil pack connections—those “easier to pull” boots might not be seated fully. Also, a misfire from an unseated plug wire can trigger traction/stabilitrak warnings. A scan tool might point you straight to the culprit.