GMC 2007 Sierra - Manual (Page 175)

Running the Engine While Parked
It is better not to park with the engine running. But if
you ever have to, here are some things to know.
{ CAUTION:
Idling the engine with the climate control
system off could allow dangerous exhaust
into your vehicle. See the earlier caution
under Engine Exhaust on page 174.
Also, idling in a closed-in place can let
deadly carbon monoxide (CO) into your
vehicle even if the climate control fan is at
the highest setting. One place this can
happen is a garage. Exhaust — with
CO — can come in easily. NEVER park in
a garage with the engine running.
Another closed-in place can be a blizzard.
See Winter Driving on page 402.
{ CAUTION:
It can be dangerous to get out of your
vehicle if the automatic transmission shift
lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can
roll. Do not leave your vehicle when the
engine is running unless you have to.
If you have left the engine running, the
vehicle can move suddenly. You or others
could be injured. To be sure your vehicle
will not move, even when it is on fairly
level ground, always set the parking brake
and move the automatic transmission
shift lever to PARK (P), or the manual
transmission shift lever to NEUTRAL.
175