[Tomakze]

Just like the title says, I'm trying to figure out how to bypass VATS for my LS swap. I have a VATS bypass (not a resistor, this sends the "everything checks out" signal the BCM usually sends to the ECU when VATS sees the right resistance value. Here's the link: GM VATS or PASSkey II Bypass Module For LS1 and LT1 | eBay

I have searched, and can't seem to find a definitive answer. I know this works on early LS1 applications, but the GTO setup is a bit different thanks to being built by Holden. I'm trying to figure out if I can use this, or if I need someone to unlock the ECU with a tuner, which costs considerably more. Thanks in advance for the info! Maybe I'll add some photos of the project, if anyone is interested... It's a mildly built LS1 and T-56 with 39k miles on it going into a 1990 Nissan Hardbody pickup truck... Should be very rowdy, and a total sleeper! Thanks for the help, guys!

 

[Deadhead926]

1. I don't THINK it'll work just because it's an Australian built "Pontiac" while I'm NO fan of spending another's money have the ECU "unlocked" if it were an '05 or an '06 you just go DOD delete & your good to go but the '04's are very quirky. I'm trying to find a USED alternator for a core exchange & recently discovered that an '04 Pontiac GTO alternator WILL NOT interchange with no other vehicle on the planet.

 

[Fox Mulder]

GTO VATS does not use a resistor, there is an actual data exchange with the key. So a resistance-based bypass module won't work and it has to be disabled with a tuner.

 

[Tomakze]

1. I don't THINK it'll work just because it's an Australian built "Pontiac" while I'm NO fan of spending another's money have the ECU "unlocked" if it were an '05 or an '06 you just go DOD delete & your good to go but the '04's are very quirky. I'm trying to find a USED alternator for a core exchange & recently discovered that an '04 Pontiac GTO alternator WILL NOT interchange with no other vehicle on the planet.

I've never had any auto parts store check if the core exchange matches... I've given them a slightly different part as an exchange several times with no issue. I'm probably going to end up doing something similar with my alternator, as it is slightly too fat for my swap, so I may end up ordering a Camaro alternator, which if my research is correct, has a slightly smaller body, but mounts exactly the same way.

 

[Tomakze]

GTO VATS does not use a resistor, there is an actual data exchange with the key. So a resistance-based bypass module won't work and it has to be disabled with a tuner.

The module I linked to isn't a resistor, it sends the "key okay" signal from the VATS module to the ECU. I know the GTO uses a different style key all together, but I don't know if that signal is the same or not. Normally, the VATS module at the ignition measures the resistance of the key and compares it to the saved data, and if it matches, it sends a signal to the ECU. This chip sends that signal, bypassing the resistor and the associated system all together. I'm hoping that has a chance of working in the GTO, but information on that seems scarce.

 

[Deadhead926]

This is an interesting post, isn't the VATS linked to the BCM, or does it "wire" to the ECU & the BCM just "reads" the signal? I have both volumes of the '04 GTO service manual let me check to see what if anything can be done. Oh & by the way post pictures it sounds like a different kind of build different being unique. What year Camaro alternator are you going with?

 

[Nothubertjfarnsworth]

Turn it off with hptuners.

 

[Tomakze]

This is an interesting post, isn't the VATS linked to the BCM, or does it "wire" to the ECU & the BCM just "reads" the signal? I have both volumes of the '04 GTO service manual let me check to see what if anything can be done. Oh & by the way post pictures it sounds like a different kind of build different being unique. What year Camaro alternator are you going with?

My understanding is there is a small device in the ignition cylinder that reads the resistance, which feeds that signal to the VATS controller (not sure if that is a separate module, or part of the BCM. I have neither, obviously, since I'm doing a swap, so I have no easy way to check this out) then the VATS controller (or BCM, again, not sure) feeds a 30-50hz signal to the ECU to say 'yup, the key checks out'. Once the ECU gets that signal, it allows the engine to operate normally. Without it, it cuts ignition 3 seconds after startup.

Not sure what year Camaro alternator is best yet. I checked the 2002 alternator, and it definitely will mount up to the factory mounts, no prob. The chassis also looks smaller. It has a weird fan shroud thing on the back of it though, and I'm not sure what that's for. No idea if wiring is different, but if it is, I'd imagine that would be trivial to change. Alternators are pretty simple, and all work on the same basic principles, generally.

 

[Tomakze]

Every time I try to upload a photo, my phone locks up... Here's a link to my profile on Instagram, it has a few photos on it! (I also build custom subwoofer boxes and do car audio professionally, and there's a fair amount of that on there as well.)

http://instagr.am/p/B8CBc68ppUi/

 

[Nothubertjfarnsworth]

My understanding is there is a small device in the ignition cylinder that reads the resistance.

it doesn't work that way in a gto. Fox Moulder gave you the correct explanation. You are thinking of an older GM security technology.

 

[Tomakze]

it doesn't work that way in a gto. Fox Moulder gave you the correct explanation. You are thinking of an older GM security technology.

For some background, I am a car audio installer for a living. I install remote starts as well. Here's why I'm so hung up on this... when I look up a 2004 GTO for remote start installation information, it gives me a diagram of how to bypass the immobilizer module (VATS). The "correct" way to do it is by soldering a wire to the contact button on the key, running that through a relay, and connecting another wire to the key shaft. Those are wired into the immobilizer wires coming out of the ignition. When you attempt to remote start the vehicle, the relay connects the contact button to the circuit, and the key shaft as a ground reference, and measures the resistance between the key shaft and the the contact button on the key. That implies the GTO does use a resistor based immobilizer. It's a different design from traditional GM keys, as it lacks the little peanut shape resistor in the shaft of the key, but the idea is the same. That guide says you should use an actual key as part of the circuit for best reliability, but it says alternatively, you can use only a resistor that matches the resistance value of the key, it just isn't considered as reliable.

 

[Nothubertjfarnsworth]

Guess it's time to dig out the service manual and see what it says.

 

[Nothubertjfarnsworth]

Service manual says that the key is coded. The BCM transmits a security code the ECM via the BCM. It says the security code is transmitted through the slip ring or remote receiver.

the way the rest of the document is worded does indicate some kind of data transmission. i can post it up later if you like. however, it's wording doesn't necessarily negate the possibility of the key using a resistor.

Can you post any documents verifying what you've posted?

 

[Tomakze]

I will try, when I get back to work. My phone doesn't want to post any photos.

 

[Tomakze]

Here's the tech document from Directed Electronics. If you look at the alternative method of bypassing the immobilizer, they use a resistor, as I said. It certainly suggests it might be possible, but it uses a different system that most GM vehicles. I'd guess this system is unique to Holden.

 

[Tomakze]

Here's the circuit from AllData. Looks like it feeds +12v through the resistor wire for the immobilizer when in the lock position, though that seems crazy, because that means there is a +12v ring around the key, LOL! That's a real head scratcher... Maybe one of you that owns a working GTO can test this?

 

[Nothubertjfarnsworth]

that's interesting. the wiring diagram even labels it as resistor signal.

when i have time i can run out to the car and stick a multi-meter on it.

 

[Tomakze]

that's interesting. the wiring diagram even labels it as resistor signal.

when i have time i can run out to the car and stick a multi-meter on it.

Right? I thought that was interesting as well. GM got all sneaky, and made the system seem far more complex than it really is. If we can figure this out, it should help the whole GTO community... I'd imagine those keys are pricey in the US, considering they only work on GTOs. This might provide a cheap work around for people that have failing VATS systems.

OH! Duh! Something just occurred to me! Of COURSE the ring is +12v! That key is a "lifetime" key, meaning it has a rechargeable battery inside! The key ring is +12v, and the key itself is ground! That charges it! Duh! Okay, so the only mystery left is what does the BCM do with that info... The old VATS systems send a 30-50hz "key okay" signal to the ECU when it recognizes the correct resistance value. If this works the same way, we are in business! If it communicates via an actual data signal, this has been nothing more than an interesting deep dive on how the immobilizer works, but I'm back to an expensive reflash. Fingers crossed!

 

[Nothubertjfarnsworth]

tried it on my 04. one probe on ring, one on the part of the shaft that was showing. tried it in all positions except start.

0 volts.

not sure why GM or holden would engineer an exposed peice of metal to constantly have power to it, though. that would be an electrical and fire hazard.

possible the BCM just grounds the circuit momentarily during the start sequence and reads the resistance.

 

[Nothubertjfarnsworth]

tried four seperate keys i have laying around. they all read approximately the same resistance. it's in the range of 200k ohms.

i would need a multimeter that is far more accurate at that level of resistance to see if they are all actually different.

so, something isn't adding up here. BCM may be very accurate in its ability to read resistance, and the resistor circuits all vary in the hundreds or thousands of ohms for individual coding, or all keys just have the same resistance and there is another method of coding, and the resistance is there in the circuit for another reason.