Jeremy C

@JimCost2014 Yes, I get what you’re saying. However, before I traded it in, my 2015 Sierra always used that braking method when towing my boat and slowing for a stop sign, stop light or slowing on the highway to exit. It didn’t matter the grade of the surface. Worked flawlessly on flat surfaces as well as on any type of grade. I’m stumped.

In drive, not manual. No warning lights or codes when scanned.

No, but my 2015 Sierra always used it before when pulling my boat when running on a flat/level surface when approaching a stop sign or light. I assumed it could tell the truck wasn't slowing enough given the amount of time I was pushing the brake when in tow/haul mode and would engage the grade braking. By holding the tow/haul button for 5 seconds to disable/enable.

By holding the tow/haul button for 5 seconds to disable/enable.

I have a 2017 GMC Sierra Denali Ultimate, 6.2, 8L90 HD transmission. When tow mode is engaged and grade braking set to active, the grade braking never kicks in when slowing to a stop pulling my boat. I had a 2015 Sierra Denali 1500 and it worked like a champ. What am I missing? I have disabled/reenabled the grade braking with the tow/haul button numerous times to make sure it’s active. No downshift or RPM increase whatsoever when slowing to a stop anymore. Help!