Question about 1986 Chevrolet Corvette

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Vats system disengages fuel injection and starter in my 1986 corvette. have checked resistence on pellet and bypassed with resistor. replaced the ecm and all relays

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  • Kim Charles Moll
    Kim Charles Moll May 26, 2016

    Hello-have EXACT same problem w/GM car!BUT;VatsII key BY-Pass does NOT-Not Help with the"TDM/BCM engaging&Thus Disables BOTH Starter&Fuel Injectors"!.:)Try 'True BY-Pass Module'@""&it WILL'BY-Pass the actual"TDM and/or BCM&Start right up"!:)



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The resistor, unfortunately, will only bypass the key and the lock cylinder, but not the TDM that is the core of the VATS system. The TDM is the one often faulty instead - as it happened to me. Here is a great write-up to build yourself a full bypass that will also bypass the TDM. It is quite easy and it saved my car:

Posted on Jan 28, 2010


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1 Answer

Chip stop working

Chip stop working ? I gather your Caddy has VATS - vehicle anti theft system , with the resistor pellet on the side of the key . It's not the pellet or the key that's bad , inside the lock cylinder there are contacts that read the resistance of the pellet . Most of the time the wires coming out of the ignition lock cylinder break . If you look under the dash near the back of ignition lock cylinder ,at the steering column you should see two wires inside a orange or a yellow sheathing .The wire colors are white , now if you take a ohm meter you can check the resistance of the pellet , stick the key into the lock an turn it to start ,check resistance at those two wires an see if they match the reading you got from the pellet ! If you get no reading one of those wires are broke , at this point you can spend a couple of hundred dollars for a new one or you can spend 50 cents or a dollar at radio shack for a resistor of the same value as the pellet an solder into the wires .

Now if it's not the lock cylinder wires you have other bigger problems , like the anti-theft module .Well then your out of luck because you'll have to take to the dealer or an ASE certified repair shop that can fix this problem .

Go on youtube an check out video on vats bypass , they will show you what I told you about .

Jan 20, 2016 | 1990 Cadillac Deville

1 Answer

How to bypass vat passlock on a gm 1986 chevrolet corvette

Hey, I had to do this to my buick. I guess its a common issue with gm's..The security system fails then it wont always start... read this over.. I did and you car make and model are on the list for this issue

Sep 12, 2014 | 1986 Chevrolet Corvette

1 Answer

Cadillac Seville 1995

If your key has the resistor pellet with the short wire on each side, I can provide a bypass procedure. The vats wires are small and susceptible to damage. You will need to access the bcm connector. Basically, you need to measure the resistance of the pellet and make a resistor that has equal resistance out of a variety of resistors in series and parallel. I can do the math on that, if you tell me the resistance of the pellet. Then you cut the two vats wires at the bcm and solder the resistor to the back of the connector. I have done this on several cars.

Jul 28, 2017 | Chevrolet Equinox Cars & Trucks

2 Answers

Resister pallet fell out of my key. How do I bypass the decoder?

Go to this link, you can do a key bypass to get around that missing pellet. On this link, is listed under "temporary fix"

Dec 27, 2011 | 1990 Chevrolet Camaro

2 Answers

I would like to bypass the security system to see if that is the problem. Also How do you measure the resistance of the chip on the key when there is only one conduct, the metal part of the key it self? I...

If all you are interested in is how to "bypass" your VATS system, it is not very hard to do. All you have to do is to measure the resistance of the "pellet" in your key and cut the wire leading to your VATS module from your ignition switch and wire in a resistor or series of resistors (available at any electronics supply outlet) to match as closely to the resistance of your key pellet as possible.

The resistance is measured from one side of the pellet to the other. The key "body" has nothing to do with it.

There is a website that provides step-by-step instructions with pictures and diagrams on how to do this. Just click the direct link below.

How to bypass the VATS (PASSKey II) system

If you want to use a "hidden toggle switch" for security, the easiest way would be to use it to break the connection between your PCM and your fuel pump relay. That way you could use a "tiny" low-amp rated switch to do the job. Otherwise you would have to use a large heavy duty switch to handle the load from your fuel pump for long periods of time.

Sep 10, 2011 | 1998 Chevrolet S-10 Pickup

1 Answer

1986 corvette no power to when key is turned Battery is at 13 volts and conections are good.

It is your vats system it is locking you out. It is not reading the ignition key chip. You can by-pass the system with $5:00 worth of parts from your local radio shack. You must read the resistance across your key chip first then go to radio shack and pick up the resistors needed to match your key chip(they will assist you mine read 1850 i have a 86 vette), twist/tie them together then solder & tape them up with electrical tape. Bend them into a u-shape, locate the the 2 wires that run to your vats logic module that is tied into your ecm, should be in the middle area of your dash next to your radio(yellow and brown in color. Cut those 2 wires and add your (radio shack) resistor series between them and happy motoring no more vats problems for ever. Good Luck

Dec 13, 2010 | 1986 Chevrolet Corvette

3 Answers

Where is my ecm located? I want to bypass the VATS.

vats can be bypassed by locating wires from key lock cylinder under dash. this is common problem with this type of system. you must determine resistence valu of key resister and cut wires ind solder replacement to ends of wires that go to vats module which is seperate from ecm module.

Apr 18, 2010 | 1994 Cadillac Fleetwood

1 Answer

What is a vat?

Vat stands for Vehicle anti-theft system. If you notice there is a small pellet in the key for your buick. That is a resistor pellet or chip, this was the first attempt at a transponder key. the ksy has one of 17 differing resistor values that is read by the ignition switch and sent to the anti theft computer. The system will not allow the fuel pump and ignition systems to get power unless it sees the appropriate resistence level within specifications.
hope that helps

Aug 26, 2009 | 1991 Buick Park Avenue

1 Answer


There are 2 factory alarms on your car...VATS is the one with the resistor pellet in the key. 1) make sure the key you are using is clean at the pellet, any dirt will incease the resistor value. 2) if you have an after market alarm, make sure its door lock output is the same as the vettes (+ ground, - ground, or relay) 3) if your cars is all factory stuff, your VATS module may be bad [the least likely). Suggest a bypass 'VATS values' and match the resistance with the value of your key 1-15. If your key has a super warn pellet, you can match the resistance value on your key to a guy on ebay 1-15, buy the key on ebay for $15 and have anyone cut it..or go to a dealer and drop $50. BTW --your starter kill delay should only be 5-8 minutes.

Jun 26, 2008 | 1991 Chevrolet Corvette

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