Elevated idle can be turned on & off. High Idle is different than elevated idle. Revs up to a higher RPM and initiated by pressing the parking brake and the cruise control buttons (at least on my yr model truck). How long did you let the truck idle for? I have my elevated idle tuned on my truck and it has yet to turn on this year as well. Most of the time its cranked in the garage but a few times at work it hasn't come one. Been waiting for it to get colder and park it outside for the night to see if it works.
mines kicked on at least a half dozen times already.
2002 GMC 2500HD, ECSB, 4WD, LB7
new style gm exhaust manifold, banks big head wastegate, PPE boost valve, banks air intake,high idle switch in cruise control, stock but not for long
EFI live tuned by me now,dps5 switch,EGT probe and autometer boost sensor,SoCal 6spd conversion
2016 GMC Denali stock for now