The neutral safety switch on a 2002 Chevrolet Impala is designed to prevent the engine from starting unless the transmission is in Park. This prevents the car from leaping forward and causing damage to the vehicle and injuries to bystanders or occupants. A faulty neutral safety switch can prevent the car from starting. Replacement neutral safety switches are available from auto parts stores and licensed Chevrolet dealerships.
Shift the Impala's transmission into park and turn off the ignition. Apply the parking brake and let the engine cool down for 1 hour.
Open the hood and disconnect the negative battery lead using a battery terminal wrench. Raise the front of the Impala using an automotive jack and support it with jack stands. Place wheel chocks behind the rear wheels.
Crawl underneath the front of the car and locate the neutral safety switch. It is on the rear side of the transmission and is a half-moon shape. It's made from black plastic and attaches to the transmission with two metric bolts.
Disconnect the neutral safety switch's electrical connector. Remove the bolts holding the switch to the transmission using a 3/8-inch ratchet and a 13 mm socket. Gently wiggle the neutral safety switch back and forth until it's free from the transmission.
Install a new switch into the transmission and reinstall the 13 mm retaining bolts. Reconnect the switch's electrical connector. Lower the vehicle to the ground using the automotive jack. Reconnect the negative battery lead and start the engine. Shift the transmission into each gear and verify that the dashboard indicator shows the correct gear position.
