Automotive and Commercial Locksmith: G.M. Passlock 1

Passlock

Introduced by General Motors on the 1995 Chevy Cavalier Z-24, the Passlock 1 ignition lock is also found on the Pontiac Grand Am, Oldsmobile Achieva, and Buick Skylar (GM's N Cars) and the Cavalier and Pontiac Sunfire (J cars), beginning with the 1996 model year.
Passlock 1 uses a double-sided, 10 cut key in a single key system. Passlock 1, designed and produced by Strattec, features a small magnet in a side bar cylinder. A Hall effect sensor is mounted on the case assembly. When the cylinder rotates, the magnet registers on the sensor's three points. The sensor electronically signals the vehicle's on board computer, and the car is allowed to start if the electromagnetic value matches the code stored in the computer. A 10 minute wait (after three unsuccessful start attempts) is programmed into the system as a theft deterrent. Any attempt to force rotate the cylinder will damage the magnet and immobilize the vehicle.
Each Passlock 1 ignition operates on one of 10 possible electromagnetic values. Adding to the security of the system, there is no way to visually identify which one of the 10 values the lock contains. Replacement locks are sold randomly. Lock repairs require a quick and easy reprogramming of the vehicle computer to match the value of the newly installed Passlock 1.

After replacing the lock, try to start the vehicle with the correctly cut key. There is a one in ten chance that the car will start.
If the new lock does not match the electronic value in the vehicle's computer, an indicator light on the instrument panel will begin flashing and the car will be disabled.
Leave ignition in the ON or RUN position.
After approximately 10 minutes, the light will stop flashing and remain on. The on board computer has been programmed to accept the new lock's signal.
The car can be started.