Tow haul

[Chevy04]

 Hey guys so my tow haul light comes on but doesn't change rpm or anything it's a 06 gmc 2500 HD 6.0

[MORSNO]

Just by pushing the tow/haul button doesn't always cause a downshift and change the RPM, it depends on the current conditions.  You need to test it under load to see if it's changing shift points or going up a steep hill.  The other thing it does is change the number of turn signal blinks if you just tap it left or right (versus full engagement of the switch) from 3 blinks to 6 blinks when engaged.

[vucelick]

Check the orange wire in the steering column.

 

https://www.plowsite.com/threads/broken-orange-wire-near-ignition-goes-up-gear-selector-lever.87409/

[davester]

Light comes on in the IP, so the switch is registering as being pressed...

And yeah, it depends on current conditions if it downshifts.  For my truck it seems to notice T/H being turned on right away, but takes longer or something specific to happen to exit T/H mode.