Park the car in a safe, open area
Turn off the engine and remove the key
Open all doors and the hood if needed
Make noise to encourage the mouse to leave
Use a flashlight to check common hiding spots
Place a humane mouse trap near the exit point
Put a small amount of peanut butter or seed bait in the trap
Remove all food, trash, and crumbs from the car
Vacuum the interior thoroughly
Check under seats, in the glove box, and in the trunk
Seal any openings, holes, or damaged weather stripping
Use peppermint oil or other deterrents in the car
Keep the car parked in a clean, dry area
Inspect the car regularly for signs of mice
Contact a pest control professional if the mouse does not leave