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Vortec computer ?? dealing with VATS.

Discussion in '1992-Present Chevy & GMC models' started by 87GMCJimmy, Jun 26, 2002.

  1. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    I'm putting a 99 5.7 vortec into my 87 Jimmy and was wondering if anybody new or could find out the answer to questions about the engine computer. What I've be told so from Howell EFI and Arizona TPI is that the engine wiring harness for 96-97 vortec's is different from those in 98-99's. Is this true? I imagine so. Can you get a computer for an 98-99 straight from GM for the 98-99 that doesn't have VATS? I know that VATS came as standard equipment in 99 but not in 98. Are there different part numbers for the VATS/none VATS computers? Are the part numbers the same between the 98 and 99, confirming that the computers are identical? Anybody have access to a GM parts catalog or know where/how I can find this information?

    Thanks as always,
    Mike
     
  2. monypit

    monypit Registered Member

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    If you are talking about theft lock then no you cannot get one from chevy without it that is that new. didn't the motor you recieved have the computer with it? and do you have the vin number if it didn't?
     
  3. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    I have the computer that came with the engine. I'm looking for a cheaper solution to disabling the Vehicle Anti Theft system then sending the computer out to be reprogrammed. People charge 4-5 hundred for the service. I called a couple of junk yards and I can get a used computer for $65. It's not looking like this would work. Do you have any other ideas for by-passing it.

    Thanks
    Mike
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Do you have the VATS box with the wiring harness? It's usually tucked away under the dash. If so, you can use it to generate the correct signal just by fooling it into thinking that the correct key is in the ignition. The only thing in the key is a resistor. If the value of that resistor matches what the VATS controller expects to see, then it sends the signal to the computer to allow it to enable the injectors.

    If you don't have the VATS controller, you can fool the computer into thinking that it's there by grounding the VATS input on the engine computer at a 120 Hz rate (twice per second) during cranking. /forums/images/icons/cool.gif
     
  5. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    Is it really that easy......I've been searching for this info for a while and nobody ever mentioned something this easy! But then again I've been talking to venders. I think I owe you a beer or two. I don't have the vats box. Is the grounding just a instant pulse, nothing special about the singnal (square,sinusoidal etc.) I looked into the remote start car alarms but they trigger the VATS box. If I have the vats box this would be fairly easy because there are only 16 differenet resistance values used.(and well published might I add) The 120hz grounding would be a pretty easy ciruit to build but does anyone sell a premade box that does this. I'm thinking that they should be out there.

    Thanks again,
    Mike
     
  6. HarryH3

    HarryH3 1 ton status Author

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    I don't know of any pre-built boxes out there to provide the VATS signal. When I put the 'vette engine into my K5, way back in 1989, there was VERY little information available out there. I had to wing it on the VATS. Leaving the line high didn't work and grounding it didn't work. So I tried just tapping it to ground while cranking and the engine fired right up! /forums/images/icons/cool.gif A 555 timer and a hidden switch will make it so that the VATS still works. Only by pressing the switch, to enable the timer circuit, can the engine start. The VATS keeps the injectors turned off if it doesn't send the right signal to the computer.

    Note that you have to start the signal before turning the key to the start position. If the ECM detects that the engine is trying to crank while the VATS signal is not being supplied, it triggers a 2-minute internal timer. This is to prevent someone that had all 16 of the resistors from just "fooling" the VATS into starting the engine. Unless they got it right on the first try, the engine wouldn't start, even with the right resistor value, for 2 minutes. /forums/images/icons/cool.gif You can also wire in a relay that prevents the starter from engaging. At least this is how it worked on the '87 'vettes. They disabled both the starter and the injectors until the VATS data was correct.
     

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