Why Do You Have to Put a Car in Park to Start it?

A key in the ignition distributes a current to start the car.

To start a car, the car's transmission gear must be positioned in the "Park" or "Neutral" position. This means that unless the car is put in "Park" in an automatic or manual car, your car will not start, no matter how hard you turn the key in the ignition.

Electrical System

The electrical system, also known as a starting system, consists of a battery that transports a small current through the neutral safety switch to the starter relay. The starter relay transmits a high current flow through the battery cables to the motor, starting the car.

Neutral Safety Switch

The neutral safety switch on an automatic transmission will block the current to the starter circuit when the car is not in "Park" or "Neutral" gear. In a standard transmission, the switch is connected to the clutch pedal to prevent the starter from transmitting the current unless the clutch pedal is depressed.

Ignition Switch

The ignition switch is the switch that accepts the key. When the key is turned in the ignition, the ignition switch supplies power to the ignition circuit and starter motor, unlocking the steering wheel and shifter. To turn the key all the way, the transmission gear has to be in "Park" or "Neutral."

References

• Family Car: The Starting System
• Samarins: Starter Motor