How to bypass the VATS (PASSKey II) system in a late model GM vehicle



This document pertains to the following vehicles:


1994-1996 Grand Prix

1992-1999 Bonneville

1989-2002 Firebird/Trans Am/Firehawk


1997-2005 Century

1994-2004 Regal

1992-1999 LeSabre

1991-1996 Park Avenue

1991-1996 Roadmaster

1990-1999 Riviera

1990-1992 Reatta


1994-1997 Cutlass Supreme

1990-1999 Eighty Eight/LSS/Ninety Eight/Regency

1991-1996 Custom Cruiser Wagon

1990-1993 Toronado

1995-1999 Aurora


1995-1999 Monte Carlo

1995-2001 Lumina

1989-2002 Camaro

1986-1996 Corvette (C4)

1994-1996 Caprice/Impala SS


1989-1993 Allante

1989-1997 Seville/STS

1989-2003 Eldorado

1990-1996 Concours

1990-1999 DeVille

1991-1996 Brougham

1991-1996 Fleetwood


This is not a comprehensive list, so it also pertains to any other GM Vehicle with the VATS or PASSKey II system.  If the ignition key looks like either pictured below, then your vehicle has VATS.

Key "A" : 

vatskey02.JPG (105926 bytes)

Key "B" :

centurykey01.JPG (96161 bytes)


If you have a 1996-2005 GM vehicle without the chip in the key and are having trouble starting the vehicle CLICK HERE  


First, to make sure you're having a VATS related problem, answer the following questions:

--  When you insert your ignition key and attempt to start the car, will the starter not crank over? 

--  Does the "Security" light flash during any time you're attempting to start the car?

If the answer is "YES" to both questions, the simple solution is to first clean off the chip on your key or try another key for the same car.  If that also does not work, then follow my instructions for a fast, simple, and relatively inexpensive repair.

Before ruling out the VATS system, be sure to first check the integrity of your vehicle’s electrical system.  A dead battery, worn or loose battery cables, or a dead starter could also cause a “no-crank” situation.

**NOTE** After performing the following procedure, your vehicle's factory starter interrupter (VATS) will be disabled.  It will be considerably easier for a thief to steal your car. 


***Now that being said, I want to stress that I am not an expert on the VATS system, by no means.  I simply stumbled across a way to bypass a malfunctioning "reader" in the ignition lock cylinder.   On my 92 LeSabre, the wires running from under the dash to the "reader" broke inside the steering column, and I didn't feel like pulling the column apart to fix or replace the lock cylinder.  Using a Factory Service Manual, I located the wires in question and created the "resistor pack" to jumper accross them.

Just to reiterate:  I am not an expert on this system, and know nothing more than how to bypass the "reader" in the ignition lock cylinder.  I can only give 100% confirmation that this trick works on W-Body and H-Body vehicles.  I have never tried the bypass on any Cadillac, Camaro, Riviera, or Corvette VATS system, so they could possibly be slightly different than what I've posted here (and the trick might not work exactly as described.)


Please follow the links at the end of this document for further help.


If you have a 1996-2005 GM vehicle without the chip in the key and are having trouble starting the vehicle CLICK HERE  



With that out of the way, here's an explanation of the VATS system (which I culled from a locksmith selling VATS blanks on eBay.)


Vats stands for Vehicle Anti-Theft System. Lots of people refer to this type of key, as a "computer Chip key". This key or "Chip" has nothing to do with a computer, nor is it a chip. But because of the popularity of calling it a computer chip key, we will also so that we don’t confuse. The black chip on the blade of the key is actually a resistor. GM first started using the VATS key in 1986 on the Corvettes, then some of the Cadillacs, etc. GM uses 15 different resistors in their VATS keys. Just by looking at the keys you can’t tell the difference.

How does the VATS System work?

Each VATS key has its own unique cuts on the key to operate the lock. But the cuts alone will not allow the car to crank. This is called a mechanical key. Each car has a VATS module (TDM) under the dash that communicates to the starter, fuel pump, and the ignition lock. Each VATS module is randomly given a number value from the manufacturer. When the proper mechanical keys, along with the proper VATS chip (resistor value) turns the ignition lock, the VATS module reads the chip on the key. If it is the correct chip, the VATS module will tell the starter and the fuel pump to operate. If the wrong chip is read, the VATS module will tell the starter and the fuel pump to shut down.

How to determine the Value of your key:

By chance you may know what VATS key you now have. Most people do not. There are basically two ways to determine what VATS key you have. Remember, there are 15 different possibilities. First, your key can be "read" in a VATS tester. Most locksmiths have these readers, and don’t change anything to tell you.  There is another way for you to read the key value yourself.  If you have a Volt Meter you can test the OHMS (resistance value) of the chip yourself.  Just set your Volt meter to check OHMS, take each lead and place it on each side of the "chip" on your key.   A number will appear. Take that number on your volt meter and apply it to the OHMS chart below. Keep in mind that it may not be exact. Just pick the closest value to your reading.

This chart is for any GM product, Buick, Cadillac, Oldsmobile, Chevrolet, and Pontiac that has a VATS key (single or double-sided.)

VATS #      (K)OHMS (Set your meter to the 20k ohm setting)

1———— 0.402
2———— 0.523
3———— 0.681


Here is a page that offers up further explanation.


Okay, onward we go!

Tools and supplies needed:

Soldering Iron

Wire Cutters/Strippers/Crimper

Voltmeter/Ohmmeter (DMM)

Approx. 8 inches of 16 ga. wire (speaker wire works great)

"Bullet-Style" solderless connectors

Heat Shrink Tubing

Resistors of varying values (totaling the resistance measured across the key's "pellet.")  I get asked quite frequently what the wattage of said resistors should be.  I've used 1/2 Watt resistors with much success.

2015 Interruption:

Now I realize that Radio Shack barely exists anymore, so it may not be as easy these days to drop by a store to purchase resistors as it was when I first wrote this document.  I would recommend hitting up the ‘ole Google-fu and searching for “The Install Bay VATS.”  They manufacture the necessary resistors for performing the VATS bypass (all 15 are contained in the kit,) and they’re all a 1-resistor deal, with no need to cobble together a series of resistors as I had originally suggested.  Keep this in mind as you read the next section…


Alright, let's begin the madness:

1.  Take your DMM, set it to measure Ohms (use the 20k setting.)   Measure the resistance across the pellet of the ignition key.  Place one probe on the silver part of one side of the pellet, and the other probe on the other side.   Write this value down.

2.  Purchase a resistor or resistors that add up to the value measured in step 1.  Radio Shack is a great place to go for the resistors, heat shrink tubing, and the "bullet-style" solderless connectors.

3.  Take the 16 ga. wire and cut into 2 four-inch pieces.

4.  Strip off approx 1/16" of insulation off each side of both wire pieces.

5.  Put your resistors together in series (or if you're lucky and have a chip that has a resistance that matches a single resistor) and solder one wire to one end of the resistor(s) and the other wire to the other side.

Example:  You measure 11.72 on the 20k (k meaning kilo or 1,000) scale.  The closest match is 11.801 which is a #15 "chip."  Always remember that resistors have a tolerance of 2%, meaning the resistance value of the "pellet" can be either 2% higher or 2% lower than 11.801 k ohms (11.72 falls in tolerance range.)  You will want to aim for 11,801 ohms.   So when you go to Radio Shack you want to pick up a 10,000 ohm (10k,) a 1,000 ohm (1k,) and an 800 ohm resistor to wire together in series to achieve the 11.801k ohm value.

Here's an example of how you'd connect the above mentioned resistors in "series"

wire------10k ohm------I------1k ohm------I------800 ohm------wire

6.  Measure the resistance across the 2 wires now that the resistors are soldered to them.  Be absolutely sure the value matches that of the resistor pellet in the ignition key (within 2% up or down.)

7.  Cut a length of heat-shrink tubing to cover up the resistors, allowing a small bit to hang over onto each of the 2 wires.   Use a lighter or heat gun to shrink the tubing.

8.  On one of the wires, crimp on a male bullet connector, and on the other wire crimp on a female bullet connector.

9.  Now what you have should look like this:

vats.jpg (38518 bytes)

Notice in the above "resistor pack" I lucked out and only needed 1 resistor to match the pellet's resistance.  You may not be so lucky...

10.  Now move to the car.  Remove the under-dash kick panel.

11.  Compare your key to the images near the top of the document.  If you have Key "A", look for an ORANGE wire running down the steering column.  If you have Key "B", look for a BLACK wire running down the steering column.  Regardless of color, this wire should have a "rubbery" feel to it, and should be separate from any other cluster of wires.

**WARNING** Do not tamper with any of the wires near the column wrapped in yellow harness tape, any yellow wire, or any yellow electrical connector.  These wires/connectors are for the airbag.   Tampering with any of these wires could result in the airbag discharging.

orangewire.jpg (42215 bytes)

The above pic is unfocused, so I've included some stock photos of various VATS ignition lock cylinders to clarify what exactly you should be looking for:


Key "A" type:

cylinder01.JPG (41919 bytes)


cylinder02.JPG (21842 bytes)

cylinder03.JPG (39033 bytes)


overview.JPG (20716 bytes)


Key "B" type:

centurycylinder.JPG (28011 bytes)

centurycylinder02.JPG (11423 bytes)



12.  Cut the ORANGE (Key "A") or BLACK (Key "B") conduit as seen above and locate the 2 small wires inside.  On airbag equipped models, the small wires inside the conduit are white.  On some of the older non-airbag equipped vehicles, the wires may be yellow.  Strip back the insulation on the wires on the opposite side of the steering column. 

13.  Install a male bullet connector to one of the 2 wires, and a female on the other.

14.  Plug in your "resistor pack" that you made by mating the male and female bullet connectors.


diagram.jpg (31252 bytes)


15.  Attempt to start the car.  If your problem was with the VATS reader in the ignition lock cylinder, this will start the car.  

If this won't start the car, then the problem is in the VATS module (also called TDM, or Theft Deterrent Module.)  Most of the cars listed here have a TDM (mainly Key Type “A.”)  Key Type ”B” vehicles will not have a TDM, however the VATS will be controlled by the Body Control Module (BCM.)

At this point, you will need to locate the TDM and replace it (Key Type “A”) or take it to a GM dealer to reprogram or replace the BCM (Key Type “B.”)  Location varies per vehicle.  Do a Google search to find where the TDM is located on your particular vehicle.

If you’ve determined that the reader in the column is fine, remove the resistor pack and splice the 2 halves of the wiring back together as they originally were to restore the function of the VATS reader.  Near the end of this document, I have posted links to sites that either sell TDM bypasses, or have plans for you to make your own.




This is what the inside of the steering column looks like torn apart down to the ignition lock cylinder. Just to the right of the steering shaft, you can see the orange "conduit" with the 2 white wires running out of it into the lock cylinder. These wires typically break off inside the column, rendering the reader useless. The purpose of this document is to save the hassle of tearing the column apart, and get the car up and running for the least amount of cost.


Another trick you could do is to locate the connector under the dash where the VATS wires plug in and solder your resistor pack directly to the connector as such:

resistorplug.jpg (68481 bytes)

Thanks to Gordon for the above image!

This is another view of the connector:

connector02.JPG (25125 bytes)


Here's a view of the connection under the dash of an 89 Eldorado (notice the wires are YELLOW) :

Wiring 004.jpg (77496 bytes)

Thanks to Joe Zerby for the image!

 This "plug" is not present on the H-Bodies (88/98/LeSabre/Bonneville,) as the VATS wires run to the bulkhead connector.   If you have an H-Body, you'll have to perform the bypass as originally described.


If you have a 1996-2005 GM vehicle without the chip in the key and are having trouble starting the vehicle CLICK HERE  


Before signing off, I have received some more info from a fellow forum member.

From WhiteMonteZZZ :

If VATS is disabled (via your site), then additional keys without the VATS pellet are able to be purchased (and used) at most local hardware stores. The keyblank needed would be an ILCO (or equivalent) B62 blank (this has GM's 'A' keyway, no resistor, and typically was used on Cadillac Allante vehicles). The original key can be cut onto this blank, but the head typically needs to be filed down at the part nearest the ignition lock 2-3 mms. The standard B62 blank will hit the face of the igniton lock, so by shortening the head of the blank, you're in turn lengthening the blank.

He also says you can trim the plain-ole ignition key down with a dremel tool.  Here is a pic he sent to me showing the new "trimmed" key:

trimkey2.jpg (35276 bytes)

You can plainly see where the key is cut by the outline drawn on the paper beneath the lower key.

Adding to WhiteMonteZZZ's suggestion, I recently received an idea from another member.  stockgp recommends using an "AXXESS" brand key, blank #4.  The head of the key is longer, and thus can be trimmed to the exact shape of a VATS key:

axxess.jpg (27163 bytes)

I've seen these keys sold at Wal-Mart in the past (not sure if they have them anymore) and stockgp says he bought his at "Busy Beaver" (in the Pittsburgh area.)  I recall K-Mart having sold these keys as well.

Many thanks to WhiteMonteZZZ and stockgp for their very helpful suggestions!


Update 1/31/15:

“Jeff in New Jersey” has written me with some very useful info on the VATS system.

From Jeff:

The car is a 98 Monte.  The SECURITY light was ON but NOT FLASHING.
The car started and drove normally.
The first thing I did after determining that my key is a 7.5K ohm was to 
unplug the connector and put the key in ignition and measure to see if 
7.5Kohm was present.  It was NOT.  The wires were broken in the steering 
Here's what I've found out about this NOT flashing security light on my car:
If the wire breaks WHILE THE ENGINE IS RUNNING the car will NOT be disabled 
because the TDM (Theft Deterrent Module, a.k.a. VATS module) interprets this as a FAILURE of the system and NOT a theft 
attempt.  The car should operate normally until such time as the battery 
dies or is replaced.  As long as the system
has battery power the FAILURE 
mode is saved.  Once the battery power is removed and restored, the Security 
light will FLASH and the car will be disabled.
This point above is very difficult to find on the internet...
If the wires break when the engine is NOT running, you will get the FLASHING 
security light, and the car will not run because this is seen as a theft 
attempt by the TDM.
Many thanks to Jeff for this discovery!!!

Update 9/26/15:

I’ve received suggestions over the years involving touching the ends of the white wires directly to the pellet in the key.  Today, with permission, I am posting another e-mail, verbatim, from Bob:

I want to thank you for your great post at regarding overriding the VATS.  I had a problem in a parking lot at 1:00AM a few days ago.  The car would not start and I was getting the "STARTING DISABLED" and "REMOVE KEY" messages.  Your post helped me with my troubleshooting and resolution.  I began troubleshooting and ruled out most possibilities, such as reprogramming the key, until I was fairly certain that the problem was in the steering column.  But at that time of the morning I did not have access to a store to get the necessary resistors.  So I came up with a temporary solution that others might find helpful.

1) I took two short pieces of thin wire and stripped all four ends.  I happened to have some solid-core wire left over from installing my garage door opener and it was ideal for what I needed because the stripped wire stayed stiff, but any light wire, multi or single strand, should work.

2) I removed the panel under the dash to get access to the wiring harness. I was able to quickly locate the two, thin, white wires with orange sheathing.

3) I took my two wires and stuck them into the wiring harness alongside the two white wires so that my two wires would make make contact with the metal leads in the wiring harness.

4) I then held the other two ends of my wires against the resistor chip in my second set of keys.

5) I tried starting the car with my primary set of keys in the ignition and it fired right up.

I had effectively created a parallel circuit that went through my second key rather than up the steering column and through the ignition switch.  It took me several tries, probably because my temporary wire was not making contact with the terminals in the connector.

I was able to let go of the wires on my second key and the car kept running just fine and I was able to drive home.  When I got home I found that I was able to shut the car off and restart it without using the trick with the wires and the second key.

HOWEVER, when I had let go of the wires on the second key the instrument panel immediately began displaying the messages "THEFT SYSTEM PROBLEM" and "CAR MAY NOT RESTART".  I assume this is because I no longer had the second key "wired" into the circuit so it no longer saw a resistor.  I read on a post (maybe on your post) that if the VATS fails while the car is running, which is essentially what happened when I let go of the wires on the second key, then the computer sets a flag that VATS has an issue BUT it still allows the car to keep running and, at least in my case, to restart.  But if I were to remove the battery cable or the battery were to run down then the flag might be reset and the car might not start because it would see a VATS failure BEFORE starting and interpret that as an attempt to steal the car.  In that case I might need to do the trick again with the wires and the second key.

Since I didn't want to keep seeing the two messages ("THEFT SYSTEM PROBLEM" and "CAR MAY NOT RESTART") flashing all of the time and I didn't want to worry about losing power to the computer, I bought the appropriate resistors and wired them into the circuit as per your post.

Thanks again for your very helpful post.

Bob Gardner

1999 Cadillac DeVille


Many thanks to Bob for his suggestion (and to the others who have suggested wiring directly to the pellet, I apologize for not posting this info sooner.)


If you have a 1996-2005 GM vehicle without the chip in the key and are having trouble starting the vehicle CLICK HERE  


Now to conclude the document, I have been shown a way to completely bypass the VATS module altogether.  The VATS module (TDM) generates a 30/50hz ground pulsed signal to the ECM/PCM to enable the fuel injectors.  There is a way to fool the ECM/PCM into seeing that signal.  You will need to build your own signal generator with parts from Radio Shack.

Here's the link to the page with the plans:


Here's a place that sells a TDM bypass module that does the same thing as the DIY version above:


I have no association with the above links, so please do not send questions regarding them.  Use at your own risk!


Also, as of 1/31/15, there is an auction on eBay for a 15-pack of resistors, each with a corresponding VATS resistance value:

This method would be much easier than cobbling together your own series of resistors.




If you have a 1996-2005 GM vehicle without the chip in the key and are having trouble starting the vehicle CLICK HERE  


Any questions or comments?  Feel free to drop me a line at  as I am always open to suggestions to improve this document.  Just be aware that I might not be able to answer your question if it's beyond what's discussed in this write-up...


Many thanks to those of you who have sent me suggestions over the years.  I truly appreciate it!  If you have found this document helpful at all, please feel free to pass it along to anybody else in need...


This page was last updated on 9/26/2015




Copyright © 2004, 2015 by Kevin Bloomquist (a.k.a. "DiscoStudd" on various GM related forums) for LikeABigDog.Com.   The text in this document may be reproduced without permission.  Images are property of the owner and may not be reproduced without permission.  All Rights Reserved