Backstory: I found an '88 Fiero with a gutless engine and plan to pack an LNF into it. I bought an '08 Cobalt SS that had been rolled over from a salvage auction and stripped it all. I'm in the process of finding out which modules are necessary to keep the ECM happy so the entire wiring harness is laid out on the garage floor. The Fiero key will be needed to unlock the steering column and (depending on what route i choose) to run lights and things. Therefore, I wanted to get rid of the Cobalt key barrel. I searched around here for engine start buttons but the only things that showed up were silly computerized modules So i did some of my own probing.

There are 5 wires going into the bottom of the key barrel (at least for my '08).
Red w/ white stripe = power
brown = accessory
yellow = run
white = key present (i think for the ding if you leave your key and open the door)
white w black stripe = idk yet but it seems to connect with key present while running

anyways...all you need to do to get your engine to start is connect power to accessory, connect power to run, and then temporarily remove power to accessory. Since the engine will crank until it's running you don't need to hold accessory off, it can just flash off and then you are good to go.

So basically you need 3 switches. Two on/off toggle switches and a normally closed momentary switch. Connect power to one terminal of the first toggle switch, jump the other terminal to your momentary switch, and then connect the other terminal of the momentary switch to your accessory lead, the brown wire. Then connect power to the other toggle switch and run (yellow wire) to the other terminal of that switch.

Flip accessory to ON (lights should come on), flip run to ON (your fuel pump should prime), and then push your momentary switch to temporarily kill accessory power and the engine should crank. Flip run to OFF to shutdown the engine.

Remember that your key still needs to be within ~3" of the ignition switch in order to communicate with the VATS antenna. And for those of you with whole cars you'll need the key to unlock the steering and everything anyways. So this probably isn't a pragmatic deal for most people but it is kinda cool.

Sad part is I couldn't find any engine start buttons online that were normally closed, they all seem to be normally open so they connect when you push them. You could label your own switch or run a relay but that seems like too much work

 

You can disable vats with hptuners. Nice work though, you should make a build thread.

 

I just realized that for people who still need to keep the key barrel anyways you really just need the normally closed momentary switch. Just put it in line with the brown ACC wire. Turn the key to RUN and then bump the button and off you go.

 

Pretty sure that disabling VATS is not going to change the car looking for the chip in the key though.

 

Thats all that vats is...

Also if the car is running and you unplug the theft deterrent module it will disable it.

 

Subbed, Good info in here to know

 

Now that you say that, you stirred my memory.
My old LSJ and my buddy's LSJ used the same keys. We swapped PCM's at one point and I had to shut of the VATS on both. From that point on we could use our own keys on eachothers car. I almost got him SO good one night when I saw his car at a local restaurant. I went and hid mine and was in the process of getting in his to move it when he came out. It would have been EPIC.

 

Did you ever find out what the white-black wire was? My understanding is that it measures a certain amount of resistance either in the key or lock cylinder. Which tells the anti-theft system that its not stolen? The reason i’m asking is because on another thread, it shows momentarily cutting power to brown wire and momentarily interrupting white wire from white-black wire. I found that what you suggested works, however i’m not sure what momentarily interrupting that other circuit is supposed to do and I don’t want to hurt anything.