GMC SIERRA 2020 Owner's Manual page 429

428 Vehicle Care
8. Start the engine. Check that
the vehicle is in 2
(Two-Wheel Drive High) by
starting the engine and shifting
the transmission to D (Drive)
and then to R (Reverse). There
should be movement of the
vehicle while shifting.
9. Shift the transmission to
P (Park) and turn off the
ignition.
10. Release the parking brake and
remove the wheel blocks.
11. Reset any lost presets.
The outside temperature
display will default to 0 °C
(32 °F) but will reset with
normal usage.
Dolly Towing
Caution
Do not tow this vehicle with two
wheels on the ground, or vehicle
damage could occur. This
damage would not be covered by
the vehicle warranty.
Dolly towing this vehicle is not
allowed with either the front or the
rear tires on the ground for
two-wheel drive or four-wheel drive,
regardless of transfer case.