VATS ( Vehicle Anti Theft System ), also known as PASS-Key ( Personal Automotive Security System )
was introduced by GM on the 1986 Chevrolet Corvette because the Corvette had become the number one target of car thieves. Corvette thefts dropped so impressively after VATS was implemented that GM expanded the system in 1988 to the Camaro, Firebird, and Cadillac Seville.
Before long, VATS was standard equipment on all Cadillac vehicles and on many other Chevrolet, Pontiac, Buick, and Oldsmobile vehicles. As the system was added to more vehicles, GM began using the terms “PASSkey-1” and “PASSkey-2” as more descriptive names for the system. From the locksmith’s point of view, there is no functional difference between VATS and PASSkey-1 or PASSkey-2, and most technicians still refer to the system simply as VATS.
The following chart is a list by model year of the General Motors vehicles that have been and are equippedwith the Vehicle Anti-Theft System :
Buick Park Avenue
Pontiac Grand Prix
The system itself operates on a very simple principal. In addition to the standard side-bar ignition, there is a resistor embedded into the key. When the key is inserted into the lock and turned, an electrical current runs through the resistor. The amount of current drop caused by the resistor is measured by a computer. If the current drop matches the pre-set value stored in memory, the car is allowed to start. If the current drop is higher or lower than the pre-set value, the vehicle will be prevented from starting – even with the correct key for several minutes. No alarm sounds and the only indication that the vehicle has been disabled is an indicator on the dash.The time delay feature was the main reason that VATS proved so successful.
Studies showed that if a would-be car thief could be slowed down, even for a few minutes, they would look for an easier target. VATS equipped vehicles soon became some of the least stolen vehicles on the road.
Originally there were fifteen different resistor values chosen for the VATS system.
These values are numbered 1 – 15, with the number one key having the least resistance and the number fifteen key having the most resistance. Due to technical problems involving the systems ability to accurately read the very low resistance of the number one key, the number one value was discontinued on new vehicles in the 1989 model year. When the system was implemented on the newer 10-cut locks in 1995, only fourteen values were used on the double-sided keys. System have allowable tolerance of 10%+-, due to natural instability of resistor. Pass Key & VATS resistance values contains below table :
|RESISTOR VALUE||CODE||OHMS VALUE|