I am wondering if you can help me.

I lost the key to my 1991 Trans Am GTA (5.7L).

I went to a GM dealer to get another, and they cut me a key after getting the codes from GM, but the key they gave me was just a regular $5 silver key. While it looks the same, the top of my key was black and plastic, with a chip inside. GM assured me my car doesn't need a chip.

Sure enough, I got home, and the key won't start the car.

I went back, and after arguing for a while, a technician who has the same car as me finally overheard me and he assured me that it does have a chip. They went back and dug deep into GM files, and sure enough, found that it needs a chip.

But here is the problem, how do I proceed. The only way GM says to go forward is to tow the car in, and they will go through the codes one by one (there are 15 of them) until it hits. This could cost me lots of labour.

Is there a way around this?

Is there a way to bypass the chip altogether, rewire the ignition?

Can I just install the cylinder from another 3rd gen and use the key that comes with that one, from a junkyard?

Can I do anything short of towing it in and looking for codes?

 

No, you can't just swap in another key switch. Your car has a VATS (Vehicle Anti-Theft System) module. It senses a given value of resistance from the chip on the key. If the module reads the correct resistance, it closes the starter circuit, permitting the starter to turn. It also sends a 5 Volt square wave signal to the ECM, which tells it that the key is legit and it's OK to open the fuel injectors.

The solution: You can try different resistance values in the circuit until you find the right one (read the tech article on VATS), or you can buy a VATS Bypass Module for around $20 on ebay.

 

Ternandes, that is indeed good news, but could you be a bit more specific?

Which tech article on VATS are you refering to, and what do you mean when you say to try different resistance values? With a regular voltage monitor, for ohms? And then what?

But more importantly, I am very interested in this VATS bypass module. I found this at ebay, will this do? VATS Bypass Module but what do I do after I get this? Is it simple enough? Should I just buy it and then repost if I have problems?

 

Here is the link to the article. Sorry, I probably should have just included that in my original post.

https://www.thirdgen.org/vats

Yes, that ebay item is the one I mentioned. You may want to have a look at your ECM to verify that it is the one you need... also you'll probably need the "Dual" model, which covers some models that the single one does not.

This comes with a sticker on it that shows how to wire it in, and there's an optional quick disconnect plug.

Good luck... BTW, I know all of this because I bought a GTA for which the PO lost the key... he destroyed the steering column trying to get the car started using a key without a chip. I am looking into a complete replacement column, complete with VATS module and the correct key... if I can't find one, I will probably use the VATS Bypass module from Ebay.

 

That was to be my next inquiry. I have not decided yet whether to get the VATS bypass, even tho it sounds amazing since you can turn it off anyway and the anti-theft goes back on.

But, if I do decide to want to keep the chip key, what is it that I need to replace? Its not just a new ignition then right? I have to get a replacement column, what does that include? Basically, I'm asking what will I have to get from another 3rd gen car ignition to replace mine, and use the key that comes with the replaced ignition?

 

Replacing the column isn't really necessary. The only reason I want to do that is because the PO pulled the whole column apart trying to get it to work, and in the process, he broke some pieces and others are missing.

The key has a resistance value. There were something like 15 different values used, so in theory you could buy one of each and try them all until one starts the car.

That would be costly, though, since the keys cost about $70 each.

I'm not sure where it is, but if you do a search you should be able to find a thread dedicated to this problem. In it there is a list posted of the different resistance values that were used. One option is to buy the resistors (about $1 each at Radio Shack) and try them in the circuit until you find the one that works.

Otherwise, you need your key and the VATS module to be somehow on the same page. So for example, if you found someone parting out a car with the same VATS system in it, you could use their ignition key switch and VATS module.

Personally, I'd rather use the bypass module, since it's less labor-intensive and there's less guesswork.

 

try another dealer. I went through the same thing and the local gm dealer cut me a key with the chip in the blade for 25 bucks and i havent had any problem with it

 

YOU can bypass the VATS without any "kit" from ebay or anywhere else. Just look at the VATS article - it has the resistance values listed. Then go to Radio Shack and buy one each of those resistors ($1 per), Then go back to the article and read about which wires to cut, insert each resistor one at a time until that dealer key starts the car, then you'll know the resistance! Now, you can either get a key made with that resistance chip ($20 at ACE Hardware), or simply solder in that resistor in your hand to those wires and you'll never need a VATS key again!

 

COULDN'T YOU JUST TREAT IT LIKE A NEW IGNITION. GO BUY AN IGNITION CYL W/KEY FROM KRAGEN OR O'RIELLYS,TAKE IT TO THE DEALER, THEY WILL MAKE A CHIPED KEY FOR ABOUT $75 DLLRS.THEN INSTALL NEW IGNITION. I'VE REPLACED THE IGNITION ON MY 89 FORMULA. IT'S KIND OF A HASSLE BUT IS PROB A SOLUTION FOR YOU. GOOD LUCK. (THAT WAS A FEW YEARS AGO SO HOPEFULLY THAT HASN'T CHANGED.)

 

NO - new ignition STILL has old VATS system - still have to find out what resistor is needed for the VATS.

Why is everyone so scared to actually WORK on their car? It's just a car - it doesn't run now, there's nothing you can do to make it worse - and you might actually get lucky and fix it! Just follow the articles, cut the wires, install the resistors until one works, WRITE DOWN the resistance number so you know, and fix it!

 

guys its really easy.... 1 replacing the column isnt necessary, 2 even if you replace the cylinder the old vats module isnt anywhere near the two.

Im not sure but the dealer might be able to narrow it down for you with your vin but thats just a rumor i heard, theyre way of "testing" is a switch board the place in line and flip each switch til the car will crank, its a 5 min job but they charge you a a ton for it. Youre better off doing it as i describe below....

1. Look up the 15 different values for resistance gm used for your year
2. go to radio shack and get a pack of assorted resistors (100 pc. carbon film resistors, 1/2 watt,5% tolerance, S/N 4029311489)
3. do some simple math, solder them together. You dont have to hit it exactly on the value just as close as you possibly can, the VATS has a variance it will accept so like i said as close as possible
4. Take off your hush panel below the steering column and find the VATS wire, (not sure the color but the tech article will tell you, mine was bright orange)
5. cut it
6. test each resistor in place til the car cranks
7. take the 1 that works and solder it in line and BAM no more VATS.

took me 15 mins, youll probably get lucky, and hit it before going through all 15 of them

HERE i even found the values for you. get a DVOM, and a soldering iron and go to work
General Motors Key Number Value (Ohms)
1. 392 (Ohms)
2. 523 (Ohms)
3. 681 (Ohms)
4. 887 (Ohms)
5. 1130 (Ohms)
6. 1470 (Ohms)
7. 1870 (Ohms)
8. 2370 (Ohms)
9. 3010 (Ohms)
10. 3740 (Ohms)
11. 4750 (Ohms)
12. 6040 (Ohms)
13. 7500 (Ohms)
14. 9530 (Ohms)
15. 11800 (Ohms)

 

Thanx a lot bro! I'll definitely do what you recommended, before I buy any bypass module from a dealer. Excellent. I will get on it this weekend, and report in this thread when done (who knows, i may be lazy and do it in a couple weeks, its getting cold, i wouldn't be driving the TA now anyway)

Does it really have to be soldered? If it will crank with just a crosswire, can't I just tape it together real well once I find the right resistor?

 

just sticking the resistor in and tapping it up will work, but for how long is the question. odds are it will leave you stranded at the worst possible time.

if you go the resistor bypass route, its best to cut the VATS connector off the old lock cylinder and solder the resistor to it, tape it up and then plug it in.

something i want to add for those that may decide to replace the VATS lock cylinder with one of the aftermarket VATS lock cylinders, don't do it.
at customers' request, i have used a few of the aftermarket VATS lock cylinders and most don't last.
you may save a few dollars now, but even if they warranty out the lock cylinder, it will still cost you more than just using a Delco VATS lock cylinder to start with because you will have to have a new key cut.
in a pinch, i'll use an aftermarket VATS key, but i really don't like doing it.

once you get it fixed and its working right, GET A SECOND KEY CUT!

 

At least use solderless connectors and crimp them.

 

my friend lost this key .. we replaced it with a new ignition lock from the parts store BUT ...."here was the ticker"

he asked if i could help him get the correct resistance so i could fool the ignition to think the key had a chip ... "by pass"

so I had him go to Radio shack and buy 20 bucks worth of different resistors ... and I had only made 2 when I found the correct one for the car .. I made a #7 by accident and BAM .. it turned on.

I already had a #3 and #12 for the 2 3rd gens that I have bypassed on my cars so I had already tried 3, 12, 1, and luckly on the #7 I got it to turn on.

Wooohooo Im good !!

p.s good luck

 

had a VATs issue with my 1997 Seville STS. What a pain in the ODB2 butt.

the 3rd gen VATs is easy to deal with. But why bother just take your VIN to the dealer and have then cut the right key with the right resistor.

 

Unfortunately, this guy went to the dealer to start off with, and they gave him a key without a chip. Apparently, if I am reading all of this correctly, his dealer gave him poor service... yes?

As far as being afraid to work on our cars, I am not at all afraid. I originally suggested the resistor bypass to him. I just wanted to tell him about all the possible solutions.

And PLEASE, if you use the resistor bypass method, solder the connections. I have seen way too many "Mods" that used the 'twist and tape' method that eventually failed. In this case it's critical, because a poor connection will increase the resistance in the circuit, which is what the VATS module is measuring.

As for me, I am still going to replace my column, because of the extent of the damage to the column that is in the car now. There are so many broken and missing parts that it doesn't make sense to repair it when I can just swap in a new column.

 

soldering is no big deal guys its fairly easy i learned to do it in 8th grade lol from my experience taping it up will work....but its not your smartest move. the only thing you should use tape for is covering your solder joints, and thats only if you cant find shrink tubing. doing it right the first time is the best thing you could do because you know you did it properly and its not gonna come apart on you later, the gun is like 10$ at autozone and they give you solder with it if i recall right, plug the gun in and then let it heat up all the way then just melt the solder over the wire, holding the gun underneath the wire so the solder soaks all the way thru the strands

simple stuff good luck

 

I agree fully, soldering is definitely the way to go. I'll just have to borrow a soldering iron, thats all.

I will post in this thread again when I decide which way to go, whether to get the VATS bypass module, or the resistors from Radio Shack.

Either way I hope it works out.