It is better not to park with the vehicle running. If the vehicle is left while running, follow the proper steps to be sure the vehicle will not move and there is adequate ventilation.
See Shifting Into Park and Engine Exhaust.
If the vehicle is left parked while running and the Remote Keyless Entry (RKE) transmitter is outside the vehicle, the vehicle will turn off after one hour. If the vehicle is left parked while running and the RKE transmitter is inside, the vehicle will turn off after two hours.
The timer will reset if the vehicle is taken out of P (Park) while it is running.
Shifting out of Park
Engine Exhaust#04-00-89-015E: Warranty Administration - Required Operating Procedures (U.S. Only) - (Jun 20, 2013)
Subject:Warranty Administration – Required Operating Procedures (U.S. Only)Models: 2014 and Prior GM Cars and TrucksAttention: GM of Canada Service Agents are not authorized to utilize this service bulletin. GMof Canada Agents should reference the General Motors of Canada Limited Service Policie ...