91 Trans Am Gta 5.7 will not start. Turns over but will not start. Have replaced everything suggested and nothing seems to work. if i spray starter fluid in the throttle body it will start and stay running. i shut it off and back to the same thing. only code i get is 46 (Fault at vehicle anti-theft system). how can i fix this????

 

Search for "bypass vats".

 

it stays running on starter fluid. makes me wonder if it's the vats.
vats can be disable in the chip.

 

You need to check for open or short to the ground in CKT 229. Circuit 229 is the Dark Blue wire between the PASS-Key Module, port A2 to Port F10 of the ECM underneath the passenger dash. If that's ok, it's a fault with the PASS-Key Decoder Module, and it must be replaced.

I have the test procedures for the module if interested...it's if the wire is good, it tests to see if the module is at fault or the ECM (rare in most cases).

 

thanks for the advice i will look at that today

 

There are several places, including ebay, Painless, etc. that sell VATS bypass modules. You need one. The resistor bypass only works if the VATS module is working, and if you starter is turning but the injectors are not firing, then you need a complete bypass module, about $20 - $50.

 

if the starter is turning, either somone bypassed the start enable relay, and the vats module is bad. or its not the vats module and something else is keeping the injectors from pulsing.

 

my '92 service manual asks if it will turn over, and if no, then it's a resistance problem, if you say yes, then it says you need to trouble shoot the vats module as the vats module is okaying the starter relay, but not sending the right signal to the ECM. from there it gives you steps to test the module to rule if it's the module or ECM (rarity).

this isn't to say that someone may not have already bypassed the relay, just under the assumption all is stock.

 

if you got a digital multimeter, you can check the VATS wire on the ecm plug. if its getting 30 or 60hz on it, then the vats module is sending the signal to the ecm. I just can remember if its 30 or 60hz. if its not getting the signal, then the vats module has given up the ghost.

 

http://www.bakerelectronix.com/products_vats/

 

which wire is this on the ECM, need to go do this on my project/problem? Thanks!

 

youll need pinout for your year to be exact. its usually the only dark blue wire in the ECM plug though.

 

ok, i know this sounds dumb but will my little digital multimeter be able to check it? do i set it to AC or DC (sorry this is my first try at being an electrician) it will go to 60 or 90 when the key is turned if working correctly?

 

depends on the settings on the multimeter, you need one thats able to read frequencies. the signal the VATS module puts out is either a square or sine wave at either 30 or 60Hz, i just cant remember exactly.

 

this is the thing i got, has positive and negative test needles.

 

Kinda hard to see the symbol right above the red ones, but it looks like it does voltage, resistance, and continuity (looking for broken wires). not frequencies. unless the one symbol i cant make out is the signal for the freqs.

 

first setting says VAC with a V with the symbol from up top on the picture under it. the symbol on the setting below is a solid line over a broken up line.

 

the attached pic shows the kind of meter you need. in red is circled the symbol for freqs.

 

its the symbol from the top 2

 

thanks a lot, im gonna go pick up a cheap meter at radio shack for that. ill find one with that symbol on it.

 

they normally run $20-$30 for the cheap ones.

 

found one for 17.99, better than wasting more time if the vats isnt at fault.