Engine Starts and Stalls Due to Secutiry System Fault on Chevrolet Monte Carlo

The engine may start and stall with the security light flashing. This is commonly caused by a failed passlock sensor which is part of the ignition lock cylinder. A secondary cause could be the ignition switch itself. Worn contacts inside the ignition switch can cause voltage drop issues which can affect the passlock system. Proper diagnoses should be performed before replacing any parts.