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VATS - DIY Roadside Assistance

This is a discussion on VATS - DIY Roadside Assistance within the General Help forums, part of the LSx Technical Help Section category; Since joining the site, I have viewed many threads on the dreaded VATS no-start issue. While working on our car ...

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    VATS - DIY Roadside Assistance

    Since joining the site, I have viewed many threads on the dreaded VATS no-start issue. While working on our car last weekend, I realized that it will soon be ten years old and although I have never had an issue with VATS, I felt that it was time to do something about it. We are probably all familiar with the VATS thread in which you hardwire a series of resistors into the harness under the driver side dash (Link for those that are not familiar: How to Bypass your VATS ). However, rather than bypass the system and thereby disable VATS in the process, I thought it better to just be prepared if VATS acts up on me while out on the road some day.

    VATS works by reading the resistance on the chip mounted in your key. On each side of the key is a small metal bar in a plastic surround that acts as an insulator. When the key is inserted into the ignition, a circuit is completed and the BCM looks for a pre-set resistance in this circuit. If the key or ignition cylinder contacts are worn, or even dirty, this can disrupt the circuit and result in the BCM not allowing the car to start. The first step is to measure your key with a DVOM by placing the probes on each side of the chip. My meter was set in auto range mode and resulted in a reading of .878 kilohms -- which is simply 878 ohms.








    It is my understanding that each vehicle has one of fifteen different chips in the key, as follows (copied from another VATS thread):


    1=392 ohms
    2=523
    3=681
    4=887
    5=1130
    6=1470
    7=1870
    8=2370
    9=3010
    10=3740
    11=4750
    12=6040
    13=7500
    14=9530
    15=11800

    Clearly, my key is closest to No. 4 which is 887 ohms. The system allows for a significant variance and this is probably a good idea as both heat and cold will affect resistance through a circuit. Stopping at the local Radio Shack on my lunch hour, I found two packs of resistors -- a pack of 330 ohm and a pack of 220 ohm, that I purchased for less than $2.50. Running the resistors in series: 330 + 330 + 220 = 880 ohms which is close enough.





    I started by trimming the wire ends in order to shorten up the length of my jumper. The ends were then bent in a loop and latched together to form the strongest possible joint before being fluxed and soldered. After allowing the assembly to cool for a minute, I slipped a piece of shrink tube over the resistors and hit it with my heat gun to seal it tight. Each end was also looped to avoid having a sharp point and then tested to check the resistance -- 863 ohms, which again is close enough.

















    I'll simply carry this in the car with me and if the VATS system ever acts up, a few minutes to remove the lower dash (I always carry tools) and some electrical tape should get me back on the road. Again, the VATS thread linked above will show you the connector that each end of the jumper needs to be inserted into to bypass the system and fool the BCM into seeing the correct resitance.
    Last edited by pajeff02; 03-30-2012 at 04:00 AM.

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    good idea but I would make a few changes if it were me. You would have key pellet 4 and the range on that is 852-942 with the target ohms being 887. Without taking temps into consideration you have a 5% variance resistor there. At 863 there is a chance that 5% would put you well below the minimum. 863*.05=43.15 so 863-43= 820. You definitely want 5% resistors but I would personally get it as close to that 887 as possible. What I don't know is how far below that minimum you have to get before you get a no start condition because even at 887 you can get below 852 at 5%.

    Another opinion of mine is that VATS is wasted technology in our cars. It was still really rough at that time. It's a system designed to fail so why not bypass it. Not only will repairing the wires in the cylinder eventually fail again but you can easily buy bypass boxes on ebay that will plug and play people past it. You're better off just bypassing it the first time it fails and either going with a better alarm system or going old school and putting a fuel pump shut off toggle somewhere on the car. That part is just my opinion though.

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    Good catch on the typo -- thanks. Only one way to check it, so we'll see if it works. If anything, the resistance of the jumper should go up as it was only around 50 degree in my garage last night when I checked it. I'll bring it in the house and test it again too with the meter.

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    Got the top half of the plug from the junk yard added my resistors there. Then ran lower half of circuit with plug to the port for odbll and can now plug and go. Or can remove plug and disable the car at will.

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    That's a good idea. Not sure why, but our local boneyards are usually devoid of F-bodies.

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    I need to do something like that
    One thing our junkyard is never short of is fbodies

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    Nice Jeff! I already had a spare in my trunk ready to go.

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    Is the vats something that will fail or may fail?

    I will definitely put this at the top of my list of things to do, if it's certain that it will fail.

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    Quote Originally Posted by 89RS&98Z28 View Post
    Got the top half of the plug from the junk yard added my resistors there. Then ran lower half of circuit with plug to the port for odbll and can now plug and go. Or can remove plug and disable the car at will.
    not a bad idea but still not really protecting your car......just ask any audio guy or alarm installer how hard it is to get around vats.

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    Quote Originally Posted by SS Camaro UK View Post
    Is the vats something that will fail or may fail?

    I will definitely put this at the top of my list of things to do, if it's certain that it will fail.
    My exact question.

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    yes....it will definitely fail at some point just due to the design of it. You'll notice the pellet in the key....when you put that in the ignition it contacts wires in the cylinder. Over time those wires wear down or break. It will fail....it's just a matter of when.

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    Quote Originally Posted by 0rion View Post
    not a bad idea but still not really protecting your car......just ask any audio guy or alarm installer how hard it is to get around vats.
    is there is a way besides turning it off by the PCM? I tried bypassing the fuel pump by using jumper and pulling out the fuel pump relay. The car cranks but it never started. the only way it start is with the vats key connect or the correct value resistance installed.

    Is there is a way to get around can you PM me some info please?

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    I'm having trouble figuring out exactly what you're asking....are you wanting a way to get around vats? Search vats bypass module on ebay......there's one on there for $15 that's a 4 wire connection that's for LS1's and LT1's. The cheapest and easiest is to figure out your pellet resistance and just wire in resistors. What I was saying is a thief doesn't have to do that to get the car.

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    Quote Originally Posted by 0rion View Post
    I'm having trouble figuring out exactly what you're asking....are you wanting a way to get around vats? Search vats bypass module on ebay......there's one on there for $15 that's a 4 wire connection that's for LS1's and LT1's. The cheapest and easiest is to figure out your pellet resistance and just wire in resistors. What I was saying is a thief doesn't have to do that to get the car.
    Nevrmind I misunderstood what you said about getting around vats. I was trying to figure out a way to bypass everything in case the VATS take a crap pass the resistance trick.

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    to do it that way would be a pain in the ass....you'd have to jump the starter and the fuel pump. Vats kills both of those on our cars if memory serves me correctly.

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    ^^ Good info -- I knew it disabled the starter circuit, but wasn't sure about fuel.

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    Quote Originally Posted by JayTA98 View Post
    Nevrmind I misunderstood what you said about getting around vats. I was trying to figure out a way to bypass everything in case the VATS take a crap pass the resistance trick.
    Only way I can figure would be to dig into the BCM curcuitry..

    I would not recommend messing with the BCM in that way as it's an "iffy" unit to begin with and made in Singapore.

    I'd stick to what the guys are saying here about bypassing your VATS..

    Just my .02
    Last edited by Smittro; 04-03-2012 at 03:51 PM.
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    I also think Jeff deserves and third bar under his tag adding him to the Tech Team..

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    Quote Originally Posted by Smittro View Post
    I also think Jeff deserves and third bar under his tag adding him to the Tech Team..
    Thanks, Smittro. When we created the Tech Team, we decided against having mods hold both Tech Team and Mod status. That's why we had to fire 0rion's ass to make him part of the Team.

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    Quote Originally Posted by pajeff02 View Post
    Thanks, Smittro. When we created the Tech Team, we decided against having mods hold both Tech Team and Mod status. That's why we had to fire 0rion's ass to make him part of the Team.
    I remember that playing out much differently than you do. I remember saying something like "if there's a lawyer as a mod then I can't be a mod" or something like that. j/k....people will believe that stuff. I was just burned out and needed a change.

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