95 Theft modual! How to bypass?

[Emc209i]

Ok so we fired up the 3.4 in the Fiero tonight and it cuts off after about a second of running. We checked all of the cam and crank sensors and they all work fine. There is good power comming from the coils and wires, and the plugs are good. Everything seems to be wired right, and all vacuum lines are correctly connected. The only thing the car is lacking right now is a Y-pipe and subsequently the oxygen sensor isn't plugged up.

The theft modual wire has 5 volts going to it when the key is on. I assume the lack of modual is killing the fuel.

So how do I bypass it? If I can't go around it where is the modual and how expensive is it. I know I can probably get around it with a reprogrammed ECM but I don't want to do that yet (but I may have to).

If anyone knows of a way to bypass it please share with me. My father thinks that maybe a resistor will work.

Anyone? Sappy?

-Paul

[Emc209i]

Ok so I've figured out that I need to use a resistor. Does anyone know the frequency. I don't want to have to use a potentiometer.

[patgizz]

is it a VATS deal where the donor car had a key in the chip?

if so maybe try a google on "bypassing VATS" - it's regularly necessary in TPI/LT1 engine swaps.

[IsaacHayes]

resistor doesn't do frequency.

IIRC it does need a certain frequency. You could build a 555 timer circuit, or buy a module to defeat it. I dont recall the freq it needs to see.

Depends on which type of theft device it is.

What trans do you have? if not the electronically controled one, that computer will likely cut timing and power to the motor as it thinks the trans is damaged and will be in limp home mode... You need to tune it..

[Emc209i]

Running a manual getrag 282.

[CNCguy]

If anyone knows of a way to bypass it please share with me. My father thinks that maybe a resistor will work.

Anyone? Sappy?

-Paul

The best way is to use a vats bypass unit. They are fairly easy to make but the easiest way is to buy a premade unit on Ebay for $25. If you use a plug to connect it, you can use it as a theft deterrent by removing it when you park the car.

http://cgi.ebay.com/ebaymotors/GM-VATS-or-PASSkey-II-Bypass-Module-For-LS1-and-LT1_W0QQcmdZViewItemQQcategoryZ33720QQihZ012QQitemZ220075155594QQrdZ1QQsspagenameZWDVW

[brian89gp]

There is a bit you can flip in the PCM that should disable that (don't ask which one, it has been way too long to remember). Otherwise the ebay link would be your best bet, they use kits like that all the time for remote start systems.

[Emc209i]

I just read that the VATS cuts all fuel entirely. So that can't be it!

I also just read that the IAC will kick the engine off if the motor spikes without the tranny sensors. So when you disengage the clutch it will shut off, so the computer will need to be reprogrammed so that the computer gived the motor time to shift. When I crank the motor I have the clutch in, and besides that there is a vacuum leak (brake booster line) so the engine spikes to 2500RPM. Do you guys think that's what's killing it? The IAC.

[OldSkoolGP]

If you were using OBD II I could help you. There you just have to jumper two wires together.

[CNCguy]

I have a '95 3100 and use a VATS bypass. If it is diconnected, it will start but die as soon as you release the key from start position. It will get fuel and fire but only during cranking. Hope that makes sense.

[Emc209i]

I understand. That is EXACTLY what its doing. I believe you are right! That's what's happening. I ordered a new mem-cal for the computer, that should take care of it. Thank you all for your help.

[Juglenaut]

I thought it was 50hz or 29hz for vats