A running engine fills a closed garage with poisonous gas, so staying inside to help is dangerous. First you must remove the danger: open the doors wide, turn off the engine and move the victim to a safe place.
An engine running in a closed garage produces deadly carbon monoxide. Before helping the victim, your first task is to remove the danger: air the space, turn off the engine and move the victim to fresh air, so that neither they nor you are poisoned any further.
Option 2. You and the victim are in a poisonous environment, so staying inside and examining them is extremely dangerous.
Option 3. The recovery position is useless if the victim keeps breathing deadly exhaust gases.
Option 4. The immediate danger is the poisonous gas, not the victim's posture.