Tech: How to bypass VATS
 

Special thanks to contributors: Tuned Performance , Tibo , scooter

The following outlines multiple methods of defeating the Vehicle Theft Deterrent System and when each method is appropriate.

Schematic of the theft deterrent system is shown below. Wire colors may vary by year. The VATS Decoder Module (also known as PASSKEY Decoder Module) is the heart of the system and is located behind the dash, mounted to the HVAC plenum just above and left of the radio, and the entire dash must be removed to gain access to it.

• The VATS module interfaces with the Ignition Lock Cylinder to evaluate whether the resistor pellet in the key is correct.
• The VATS module controls the start relay ON/OFF function.
• And the VATS module controls the engine ECM fuel injector enablement.

The system can be defeated several ways depending whether you keep or remove the engine ECM.

I have the stock engine ECM

See Method A. In this scenario you keep the system in tact but trick the VATS module into believing that the correct key is being used. This is done by permanently installing a resistor in the resistor sensing circuit. The resistor must be a match to the resistor in the key pellet.

I am removing the stock engine ECM

In this scenario the stock engine ECM no longer controls fuel enablement (because a different fuel system exists) but the VATS module still has control of the starter motor relay. The VATS module must be defeated to allow the starter to crank the engine.

The only reason the start relay exists is so that the VATS module can prevent engine starting as part of the anti-theft feature. The start relay serves no other function and can be bypassed safely. There are several options,

1. Do nothing and keep the theft deterrent system in tact. VATS module will operate the starter relay as long as the resistor pellet in the key is a match.
2. See Method A. Install a resistor in the resistor sensing circuit. This will negate the need to have the correct key pellet, but still relies on the VATS module to operate the start relay.
3. See Method B. Bypass the control side of the start relay. This effectively eliminates the VATS module but keeps the start relay in tact. The start relay will be controlled directly by the ignition switch.
4. See Method C. Eliminate the start relay. Both the VATS module and start relay are eliminated, and the starter solenoid is hard wired to the ignition switch.

I am doing an LS swap and the new PCM has VATS

See Method D. Disable VATS in the LS engine PCM, and bypass the VATS hardware on the car.


Schematic from 1988 Firebird service manual

https://lh3.googleusercontent.com/JV...FBE4s9ZA=w2400



Schematic from 1992 Camaro service manual

https://lh3.googleusercontent.com/Ry...sS_9g7Jc=w2400

Tech: How to bypass VATS
 

METHOD A

Measure the electrical resistance of the pellet in your key. Refer to the table below to determine the corresponding Key Blank Number, and purchase a resistor that falls within the allowable tolerance (max, min) as shown in the table.

Find the wire pigtail from the Ignition Lock Cylinder under the steering column. Disconnect the pigtail and install the resistor between the colored wires on the vehicle side of the harness. The old pigtail to the Ignition Lock Cylinder will not be re-used and must remain disconnected. The new resistor will satisfy the VATS module and allow the engine to start when the key is turned to the CRANK position. Having the correct pellet in the key is no longer necessary.

Even more elegant: Cut the pigtail to Ignition Lock Cylinder and solder the resistor between the wires. Now you have a "plug and play" resistor that can be plugged back into the vehicle harness, or removed if you want to disable the vehicle.

https://lh3.googleusercontent.com/3s...N-ZHV2N0=w2400


METHOD B

Ground the field coil of the start relay. Outcome is the start relay will be ON (starter cranking) when key switch is in the CRANK position.

Option 1: Ground the field coil locally at the start relay. Cut the small (16 gauge) DARK GREEN wire on earlier cars (BLACK / YELLOW wire on later cars) and ground it to chassis. Start relay is located behind the driver side kick panel, often down near the carpet line.

Option 2: Ground the start relay at the VATS module. Jump together terminals A3 and B1 at the VATS module electrical connector. A3 is the wire from start relay, and B1 is the ground path that the VATS module would have used if still working.

https://lh3.googleusercontent.com/iv...fBRTKlPI=w2400


METHOD C

Unplug the start relay from the electrical connector and discard. Jump the larger 12 gauge YELLOW wire to the 12 gauge DARK GREEN / WHITE wire. Start relay is now eliminated and the ignition switch is wired directly to the starter solenoid when key is in CRANK position. Note: The wire leads should be insulated to prevent accidental short to ground and possible fire. Picture below does not have adequate insulation.

https://lh3.googleusercontent.com/PX...hgOPJRhM=w2400

Tech: How to bypass VATS
 

METHOD D

• Use your choice of software to disable VATS in the LS engine PCM.
• Bypass the original VATS hardware in the car. Refer to instructions in Post #1 for, "I am removing the stock engine ECM"

Examples of editing VATS in software:

C.A.T.S. Tuner
https://lh3.googleusercontent.com/xn...-D2NnanY=w2400


Tuner Pro
https://lh3.googleusercontent.com/Ys...eOgD44oU=w2400


HP Tuner
https://lh3.googleusercontent.com/YD...k6H2feeo=w2400

Re: Community effort - defeating VATS sticky
 

A sticky that covers how to fix the VATS system would make sense. I'm not really in favor of tutorials on how to defeat an anti-theft feature. Wouldn't really want it to be a sticky for the same reason I generally don't provide step by step instructions on how to roll back an odometer.

I applaud the reasoning, and the effort, it's just information with potential for misuse. :2cents:

Re: Community effort - defeating VATS sticky
 

:huh: HUH?!?! Not even remotely in the same ball park as an illegal activity of rolling back the odometer.

It is a basic, common, and necessary modification for people that upgrade or change engine management system. And it is probably in the top 3 questions asked in this particular forum.

Re: Community effort - defeating VATS sticky
 

Explaining how to defeat VATS is the same as explaining how to start a later thirdgen without the proper key. While there are legit reasons a person may want to do that, the information can be abused by someone with less honorable intentions. I disagree with spoon-feeding a tutorial to anyone with the ability to search Google and read the first result. It should be difficult to defeat. To make it less difficult is to compromise an anti-theft feature on countless member's cars. It should be considered how it may negatively impact the community.

Just throwing it out there.

Re: Community effort - defeating VATS sticky
 

You're arguing for secrecy about an antiquated 30 year old technology. If you made this argument 25 years ago then you might get a sympathetic ear. These days defeating VATS is just part of the hot rod culture.

Re: Community effort - defeating VATS sticky
 

Must not be too obsolete if it creates problems for hotrodders. Anything that inconveniences a car thief is going to make a car a less attractive temptation. While the functional value of the system isn't valuable to you, it may be valuable to someone else, and you should take that into consideration before publicizing how to defeat the system. You're welcome to disagree, but that doesn't make my opinion any less valid. :2cents:

Re: Community effort - defeating VATS sticky
 

It is already in the How To section of the site, https://www.thirdgen.org/vats/

This thread is more tailored to the engine swap crowd, hence the larger variety of circumstances and methods up to and including integration of VATS with LS1 PCM.

You know I'm not a moderator and can't make stickies anyway. ;)

Re: Community effort - defeating VATS sticky
 

Do people ever look at the main page and how-to's anymore? :lol:

I found that being a moderator caused an awful lot of bellyaching when I was being mildly abrasive. ;) I retired my moderator status when I was living without internet access and really couldn't keep up with the job.

But anyway, I've voiced my position on the topic, so I'll leave it at that. :thumbsup:

Re: Community effort - defeating VATS sticky
 

I can take a picture for Method A of the connector on the column where you install the resistor. Other than that, you need an ohm meter so you can measure the resistance of your existing key pellet.

Method D, you just need to remove the VATS module and ground that wire that goes to the Starter relay. You should also point out that the wire colors may change through the years, as the wire in my 92 is not dark green.

Also, that wire is where someone would want to add a security feature, such as an aftermarket alarm. My alarm system will ground that wire when the system is disabled.

I am not sure Method E is a possibility with the LS. I think the output on the later VATS is different than our cars.

Re: Community effort - defeating VATS sticky
 

Here is a chart for method A

https://cimg7.ibsrv.net/gimg/www.thi...3666d05ae.jpeg
Vats can also be bypassed with a hz modulator depending on ecm a 30hz or 50hz signal .

Re: Community effort - defeating VATS sticky
 

^^^
:welcome:

Also can't have a good sticky without the wiring schematic

https://cimg2.ibsrv.net/gimg/www.thi...b01066df93.jpg

Re: Community effort - defeating VATS sticky
 

@tibo what year is that I don’t recognize the colors of the enable relay wires.

https://cimg5.ibsrv.net/gimg/www.thi...f14d643f8d.gif

https://cimg8.ibsrv.net/gimg/www.thi...6c2497d16.jpeg

Re: Community effort - defeating VATS sticky
 

I believe it is late, as those are the colors in my 91 and 92 Firebirds

Re: Community effort - defeating VATS sticky
 

So later years ground blk/yellow wire to activate the relay.

Re: Community effort - defeating VATS sticky
 

https://cimg9.ibsrv.net/gimg/www.thi...2b1cad5a5f.jpg

Pretty sure that's a scan from the Chilton's manual, so mayhaps it is, mayhaps it ain't, but they think it's a 1992 diagram.

Re: Community effort - defeating VATS sticky
 

Its specifically for a 92 Camaro so should be fine for the 91/92 as far as colors.

Re: Community effort - defeating VATS sticky
 

True dat.

Re: Community effort - defeating VATS sticky
 

What are your thoughts on including a section on how to install a VATS bypass module? Something similar to ? I didn't wind up using mine as I decided to ditch TPI and the ECM, but it did seem to work. I can get a picture and write a brief description if you're interested.

I'm thinking this could be presented as a viable option to the resistor bypass.

Re: Community effort - defeating VATS sticky
 

The VATS or PASSkey system for our cars doesn't need any fancy module to bypass it, you just need the appropriate 5 cent resistor from the table tuned posted and possibly a new prom burned if you have the stock ecm.

Re: Community effort - defeating VATS sticky
 

OP is looking at doing options, so why rule this one out?

I have that style bypass on my dirt car. Works great. I deleted most of the factory column and key switch so this worked perfect for me. Not the best option for everyone, but again, why rule it out?

Its a legit option.

Re: Community effort - defeating VATS sticky
 

Yes, please.


I'm not sure either. I have a faint memory of Pocket explaining it but I could be wrong.

Re: Community effort - defeating VATS sticky
 

Absolutely. Thank you.

Re: Community effort - defeating VATS sticky
 

It would be great if somebody could provide screen shot of turning off VATS in HP Tuner for the LS crowd.

Re: Community effort - defeating VATS sticky
 

Here is a example of tuner cat and tuner pro sorry about the resolution.

https://cimg4.ibsrv.net/gimg/www.thi...b36fee723.jpeg

https://cimg3.ibsrv.net/gimg/www.thi...32336b60b.jpeg

Re: Community effort - defeating VATS sticky
 

What you would have to do is... Throw away the Passkey/VATS box in the thirdgen, and then.... This is where it gets fun, you'd wire the 4th gen BCM into the Thirdgen dash to detect the key value, and generate the signal for the ECM. Didn't really look too close at the LS1 starter diagrams to see if they use the starter enable relay.

It wouldn't really be worth the trouble. Yes, the 98-02 BCM can be wired into a thirdgen, but it's not exactly easy. To make things work right, you're rewiring the fuse box, power locks, hatch release, headlight switch, blah blah blah. It'd really only be worth the trouble if you wanted the other features of the BCM in a thirdgen. :waveman:

Re: Community effort - defeating VATS sticky
 

Yeah, I agree this isn't the best option for most people - but why not be thorough? Also, the VATS bypass will work even if the original PASSKEY module is damaged or missing, which might be a big deal for someone with a hacked up harness or for someone swapping to TPI.

It's worth noting you still need to bypass the start relay. The bypass module simulates the signal from the PASSKEY module to the ECM which allows the injectors to fire - but it doesn't control the start relay. Think of it as sort of a hybrid of Method A and Method B.

I'll grab a couple pictures and do a step by step writeup tomorrow. It's not too complicated to install (one or two wires to 12V+ depending on whether you need the 50Hz or 30Hz signal, one grounded, one to a specific wire on the ECM).

Re: Tech: How to bypass VATS
 

Got a round of updates done tonight. Keep the good info coming.

Re: Community effort - defeating VATS sticky
 

Example of modulators you can buy
http://www.bakerelectronix.com/products_vats/
https://m.ebay.com/itm/GM-VATS-or-PA...gAAOSw3fZZ6JWY
http://www.painlessperformance.com/Manuals/64024.pdf

Re: Community effort - defeating VATS sticky
 

HP Tuners

https://www.thirdgen.org/forums/atta...1&d=1523363624

Re: Community effort - defeating VATS sticky
 

I will use it if you have it.

Re: Tech: How to bypass VATS
 

https://cimg6.ibsrv.net/gimg/www.thi...73a248649.jpeg

https://cimg7.ibsrv.net/gimg/www.thi...fa6a04747.jpeg
Bottom image from a 4th gen

Re: Tech: How to bypass VATS
 

Updated. I put all pictures on this site's picture host so links are never lost.

Moderators... This is ready to become a sticky.

Re: Tech: How to bypass VATS
 

Nice thread

Would you like to add 89-92 ecm diagnostic the pins you can read the 2.5v on or hz signal at the ecm ?

1227165 (86-89) tpi maf
Pin b6
1227730 (90-92) tpi and 3.1l
Pin f10
1227846 (89-92) tbi
Pin b6
All using a dark blue wire for passkey wire to ecm.

If you suspect the vats being a issue you can check for power at these terminals or if you have the means to read a hz signal you can measure it at the above pins.
On tbi you can remove the prom and the engine will start but run poorly in limp home mode.

Re: Tech: How to bypass VATS
 

I don't know what that means so the answer is probably yes. Besides the fact that I explicitly trust what you say anyway.

Re: Tech: How to bypass VATS
 

LOL Except for that time when all the locally hosted images got lost :p

Ya know, what a lot of other forums do is put a list of related tech threads with links, in a single sticky. That way you don't have 75 stickys at the top of the forum.

Re: Tech: How to bypass VATS
 

Looks like all 3 moderators for this section haven’t been active for years.
You might have to contact j.t to make the sticky happen.

Re: Tech: How to bypass VATS
 

Good stuff, maybe sticky this in the engine swap section.

Re: Tech: How to bypass VATS
 

I ran across these two PDFs and they were helpful to me, I think they're worth sharing.
http://www.lockmasters.com/site/pdfs...%20Article.pdf
http://my.cardone.com/techdocs/pt%2077-0011.pdf

Re: Tech: How to bypass VATS
 

If you are keeping the pasakey module with your engine swap make sure to ground the module through the c207 connector. Pin m on my car but it will be the black/white wire. Looking on the 92 schematic above it grounds through the c100 connector.

If the module is working you will get the security light for a second or two when you first move the key to run position, then it will go off. If you have the right key or resistor in place when you move it to start the starter relay will be grounded and starter will engage. If you have the wrong key the security light will come on and disable the starter for 10-15 min or so.


https://cimg5.ibsrv.net/gimg/www.thi...9ce2a6eb17.jpgC207 with port m grounded
https://cimg7.ibsrv.net/gimg/www.thi...e9ff77332d.jpg

Re: Tech: How to bypass VATS
 

Thanks for the info. Nice community effort here. This thread should be a sticky.

Re: Tech: How to bypass VATS
 

I am try to install a module vats bypass could you help me please

Re: Tech: How to bypass VATS
 

Re: Tech: How to bypass VATS
 

Re: Tech: How to bypass VATS
 

According to both those schematics, the VATS fuse only powers the VATS module

Re: Tech: How to bypass VATS
 

Re: Tech: How to bypass VATS
 

thanks scooter and tuned , this is what i thought also :thumbsup:

Re: Tech: How to bypass VATS
 

This should be linked to every 3rdgen FB.. So much bad info there..

Re: Tech: How to bypass VATS
 

I would really like to strangle some of the people that give out advice on the FB pages.