VATS VOODOO: PASSlock workaround questions:

Discussion in 'Audio + Electronics' started by Biggun, Jan 27, 2020.

  1. Biggun

    Biggun Newbie

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    As I stated in my introduction, I am new here so please forgive me if this topic has been hashed-out ad nauseam--

    I recently acquired a 1998 Chevy Silverado K3500 crew cab. The previous owner gave up on trying to make it run after having spent a small fortune on replacing ignition and fuel components, but I got it to start and run with a little research, patience and a 2.2k resistor.
    In troubleshooting the problem, most of the sources I'd run across with "fixes" or workarounds for a failed PASSlock system were/are basically "try this, and if that doesn't work, try that" and typically included a collection of schematics which run the gamut from a single resistor to a circuit block with one to three relays, resistors, and maybe a diode or two for good measure. Some say the car has to be started, some not. Some say to measure the resistance between the signal and ground leads, then swap polarities, then take an average of the two to arrive at your required resistor value. One article just flat-out said to use a 2.2k ohm resistor in the circuit. One thing the articles and YouTube videos typically had in common was that they all ended with something along the lines of: if none of that works, you'll just have to take it to the dealer.
    The resistor I put in the circuit allowed it to start and run, and the truck continues to start and run. But the gist I get from the various sources and differences in tech articles on the subject also makes me think that there could be more than one ghost in the machine. One of the first things I ran across in my search for answers was a company called "New Rockies" who make a magic-dingus box that promises to solve all of (our) VATS problems for ever and ever. The site seems sort of AMWAY-ish with all the satisfied-customer testimonials and over-the-top gushing about how great their product is. In their sales pitch, they claim that the "other" bypass solutions aren't any good because they only address the input problem (the ignition switch signal) and not the output problem (from the PASSlock decoder module to the ECM). Then of course they put forth a fallacious appeal to fear that if you don't buy their magic box, you've only fixed part of the problem, and it's most certain that your car won't start at some woefully inopportune time in the future, placing you and your family in great danger. Or whatever. But it does make me wonder. The fixes for this issue aren't cut and dry as evidenced by the various hacks to attempt to get around the problem. And as the saying goes, "it's not paranoia if people really are following you".
    So, if my little resistor fix works now, is it foreseeable that it could suddenly NOT work in the future? And if so, why? Does the failure of the decoder module to recognize a signal from a BRAND NEW key sensor indicate an impending problem with the decoder module? If so, why?
    The ignition switch and the decoder module are two different things, and they each have their own probabilities of failure at any given time independent of one another, but the whole pat your head and rub your belly at the same time and maybe it'll work approach to this fix is indicative (to me) of a correlation in failure rates between the two, which leads me to believe that the culprit may be that a drift in tolerances of the components within each of the circuits may be to blame for their eventual communication breakdown. So maybe the New Rockies Super-Big-Whooptie-Do magic box really is the solution to completely fixing the problem? Or have I just tasted the Kool-Aid?
     
  2. df2x4

    df2x4 Domestics only.

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    You're right, there are several ways to go about dealing with disabling the PassLock/VATS system in these trucks. You're also right about the majority of them just fooling the system into working. Unfortunately the New Rockies unit also falls into that category.

    What I can tell you for sure is that the absolute best/cleanest way to eliminate PassLock entirely is to have it disabled in the PCM tune. Either find someone local with HPTuners, or get in touch with a mail order tuning company like Black Bear Performance. They can disable PassLock/VATS in your tune, which will prevent the PCM from even looking for the signal from the rest of the system prior to starting.

    I can vouch for Black Bear Performance personally, they're great people to work with. A mail order tune from them is around $350 but they might be willing to do just a PassLock/VATS removal for cheaper, not sure. There are several other mail order companies who can probably do this too such as Westers, Nelson Performance, and PCMsforless.
     
  3. someotherguy

    someotherguy I'm Awesome

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    I'm not an expert on the system but since it works based on a resistance reading, any significant drift from that value results in failure. IMO that's why the system fails in the first place - as connections age, resistance increases, it starts failing intermittently and then finally complete failure.

    Tuning it out of the PCM is the best bet, along with adding a quality aftermarket alarm/antitheft system installed by a pro that knows how to "hide" the unit so a thief can't just quickly reach in and snatch it out/bypass it. Losing Passlock is no great loss - it won't stop even an amateur thief, but it will leave the vehicle's legitimate owner in a bind when it craps out.

    Richard
     
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  4. Chevy-SS

    Chevy-SS Newbie

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    I had a '98 K1500 that drove me crazy with this issue, until I found the simple bypass trick (pic below) where you cut one of the wires under dash, measure resistance with key on, then solder matching resistor into two wires. It sounds like this is this bypass method you used. I will say, it worked PERFECTLY for me. I had the truck for a number of years after I did the bypass trick and it never failed me.

    I had asked local dealer and a few repair shops and they were quoting me HUGE $$$$$'s to fix this, LOL. I fixed it myself for $2 spent at Radio Shack and about an hour of my time.........:)

    [​IMG]
     
  5. Flying Skunks

    Flying Skunks Newbie

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    I had BlackBear eliminate the vats/passlock in my '98 . Well worth it , and what BlackBear can do for our trucks is Awesome. I have sent mine back in several times for changes I have made , always a Fast turn around
     

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