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How do you disable the VATS in a 1991 Reatta?


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Measure the resistance of the key pellet.

Wire (solder) a resistor of that value (+-5%) into the two white leads coming from the key tumbler to the large steering column connector.

The wires (two) going TO the tumbler must be cut, and the resistor wired to the connector pigtails, otherwise the new resistor and key chip together, will give the VATS circuit the wrong reading.

See attachment.



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From what I've seen, the VATS is very reliable, BUT when the contact tabs on the "chip" wear down, they might not make full contact with the contacts inside of the ignition cylinder. THAT will act just like you put a regular key in the cylinder and were trying to start it.

There were about 14 different resistance values, which each generated a GM part number for the particular key. Even more variations if the key had had a divisional logo on it, although the resistance values would be the same from carline to carline.

When the systems were new, we had one new Corvette that had some issues. End result was a "fix" similar to what was mentioned as everything checked out in the diagnostics of the system. It might be advisable to consider such " inline resistors" as many dealers, as GM hasn't used that system in quite some time, might not know where they "stored" the decoder box (to determine which key chip code the particular key had . . . BEFORE a new key was cut for the car). Adding some other sort of starter-interrupt system, in combination with a keyless entry system, might also be advisable as the original system would now be deactivated.

The stand-alone computer for the VATS system is "under-dash", somewhere. That's where the master resistance value is stored which the key's resistor must match before the car will start. It MIGHT be possible to completely remove the complete system, but that might be a "last resort" sort of thing as the inline resistor is a much easier way to go.

Just some thoughts,


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