GM VATS Pellet Inserted Chip
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GM first introduced VATS in 1985 on the Chevrolet Corvette, and after proving successful, was later introduced in other models in later years.

Operation is fairly simple, The most obvious part is the key.  The ignition key as a little "chip" in it.  This is a resistor "pellet".  There are 15 possible resistances, therefore 15 different types of keys each with a different resistance.  This reduces the likelihood of a potential thief from having the correct resistance resistor on hand. Then you have to have a special lock cylinder to "read" the key.  Next is the VATS module.  It does most of the security work.  It is the "brains" of the system.  The module is what actually "reads" the resistance, but has to do it via the contacts in the lock cylinder and the related wiring.  Think of the module as a Multimeter, and the wires and contacts the Multimeter Leads.  The module reads the resistance and determines if the resistance is the correct value before the vehicle will start.

Bypassing GM Vehicle Anti-Theft System (VATS )

Vehicles with the GM VATS (Passkey) system have a resistor embedded in the ignition key. If the VATS decoder module does not measure the proper resistance when the vehicle is started, the starter and/or fuel pump may be disabled for up to 10 minutes. There are 15 possible values used in these cars. The "VATS pack" is DEI part # 652t and contains all 15 values.

The VATS wires will be two very light-gauge wires coming out of the steering column. The colors of the wires vary, but they are often contained in orange, black, or gray tubing. Determine the value of the resistor in the key. Then follow the diagram above to bypass VATS during remote start operation. If the BLUE status output has been programmed for factory security re-arm, use the BLUE/BLACK Ignition 2 output to control the relay.

NOTE: When connecting to the VATS wires, it is not important which wire is cut but make sure that the key side of the cut wire goes to terminal 87a of your relay and the car side of the cut wire goes to terminal 30.