GMC 2003 C4C042 Owner's Manual page 121

Running Your Engine While You're
Parked (Automatic Transmission)
It's 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."
Also, idling in a closed
carbon monoxide (CO) into your vehicle even
if the fan is at the highest setting. One place
this can happen is a garage. Exhaust
--
CO can come in easily. NEVER park in a
garage with the engine running.
-
Another closed in place can be a blizzard.
See "Blizzard" in the Index.
2-46
-
in place can let deadly
--
with
CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
Don't leave your vehicle when the engine is
running unless you have to. If you've left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure your
vehicle won't move, even when you're on fairly
level ground, always set your parking brake and
move the shift lever to PARK (P).