GM VATS (why your mid 90s Cadillac hates you & won't start)

VATS was the best worst idea GM ever had. Imagine you went back in time to the late 80s where most cars could be easily stolen using a screw driver. Most car companies used simplistic, easy to pick keys and there were only a few key combinations so it was easy to create a master-key set and go around stealing people's cars.

GM's response starting with their most expensive models was to incorporate a new security system that would disable the car if someone tried to start it without the correct key. The public, still believing that computers would give them a utopia instead of a dystopia, were amazed at these futuristic keys with "chips" in them.

There's just one problem. The whole design was terrible. The chip was a lie, it's really just a resistor, and the entire system was prong to failure even when new, and could not be by-passed by your mechanic or dealership. Like most 90s & up automotive electronics, the build quality is terrible. The computers and modules involved suffer from capacitor failure, solder joint failure, and tin whiskers (explaination here). The entire supply of new-old-stock VATS parts is gone and GM hasn't made these parts in years.

That means once your VATS system starts giving you problems you're screwed.

If you're lucky, the part that has failed will be the ignition switch module that reads the resistor in your key. This can be bypassed by measuring the resistor of your key, disconnecting the module from your ignition switch, and soldering a resistor of equal resistance across the connector's two wires. You will need a good quality digital multimeter to measure the resistance, or get your dealer to tell you what resistance your key used (since the VIN may tell them this information).

Once you do this any key, even a normal one, cut to the right shape will start the car. No more fake-"chip" and its associated problems.

But if that does not fix your problem or eventually VATs starts leaving you stranded somewhere again, you now need to bypass the entire system. It will cost you a few hundred dollars and I have not yet installed one and cannot walk you through it. New Rockies claims to sell a complete system bypass kit, I have not used it and can not vouch for it one way or another.

Here's the technical explaination: The VATS system talks to the car's "body computer" and tells it to disable the car. When this happens it (1) disables the fuel pump, (2) fuel injectors, and (3) the master-computer (ECU/PCM) will not fire the injectors. You can bypass the first two things to get them to work but you can't beat the third. Some years the VATS module is actually built into the body computer (which was called different things from GM depending on what year & model your vehicle is).

A complete bypass, therefore, needs to actually replace the VATS module (if it is a separate unit) or the entire body computer (if it is not) to get the car to work again. You cannot simply wire around it, since your fuel injectors will not fire.

A failing body computer may do more than leave you stranded from VATS-acting up. It can also cause your interior lights or turn signals to act in strange, unpredictable ways. You might loose turn signals or hazard lights for example. When this happens you need to acquire another one or have yours rebuilt and tow your car to a dealer that still has the ability to reprogram older GM cars to get it all running again.