Disable VATS - 2004 GTO - Questions

I am in the process of performing some experiments on the modules in my 2004 GTO...

To begin, I removed the PIM with VATS disabled (turned out that VATS was already disabled by a tuner years ago) then attempted to start the engine. The starter wouldn't even cycle.

What I am thinking - without the PIM plugged in, the starter relay is unable to receive the needed ground signal to pin 86 on the relay through the PNP Switch because the PIM is unable to pass the security signal to the PCM, which then sends the ground signal from the PIM through the PNP Switch to the starter relay post. From what I gather, the PIM's two primary functions are to convert the UART Serial Data (BCM language) to Class 2 Serial Data (PCM Language) and perform the security ?handshake? with the BCM and with the PCM. Even with VATS disabled for the car to start, it still requires the PIM and PCM to be security linked where it can deliver the ground signal to the starter relay OR have a separate ground signal being sent, whether it is decided to always be grounded or through a safety device (PNP, CPP, etc). This is my interpretation of what is occurring, but I could be very mistaken.

To prove some of this, I installed a spare PIM that I have on-hand, and the key wouldn?t cycle the starter either. What I am wondering now - if I supply a ground signal through the PIM connection plug (position 8), will the starter cycle when I turn the key to ?Start?? I am sure it will, but I think there would be a slew of codes since the BCM and PCM couldn?t openly talk because the interpreter (PIM) wouldn?t be present in the system to convert the data.

I also plan on removing the BCM to see if it will start with the linked PIM back in place with VATS still disabled.

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2 questions:

1.) When people are installing this engine into another chassis, are they just providing an alternate ground signal to the starter relay on pin 86 (with or without an intermediate safety device), allowing them to remove the PIM and BCM altogether and rely solely on the key to initiate the starting cycle?

2.) When VATS is disabled in the tune, does it only disable the need for the BCM? I?ve read that on other platforms, a resistor/key mod was still needed to allow the vehicle to start even though VATS was disabled.


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Thanks for any input regarding this topic.

I realize I am not breaking any new ground with all the swaps going on everywhere; I am merely trying to do my own testing so that I have a better understanding of the electronic system with my car. It is all very interesting to me? maybe one day I will be able to understand the coding behind the scenes? one step at a time!

hptuners only communicates with the vcm. not the abs, or esc, or tcs, or bcm, or ddm, or pdm, or any other module. just and only the vcm. like a generic scantool. And when the motor gets swapped into other cars it usually only gets wired enough to run. the cars that get these swaps typically don't get the bcm also. the kind of cars it gets swapped in already have their own ignition switch assembly and pnp switch and wiring. But usually this is the screen where you disable vats in the vcm on your 2004..

http://i1050.photobucket.com/albums/...toWiz/vats.png

you'd just disable it here and the car will start and run. Now if your starter control is run through your bcm then that is an additional security feature but has nothing to do with that ls engine or it's ecu outside of that car.

Quote:

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Originally Posted by AutoWiz

hptuners only communicates with the vcm. not the abs, or esc, or tcs, or bcm, or ddm, or pdm, or any other module. just and only the vcm. like a generic scantool. And when the motor gets swapped into other cars it usually only gets wired enough to run. the cars that get these swaps typically don't get the bcm also. the kind of cars it gets swapped in already have their own ignition switch assembly and pnp switch and wiring. But usually this is the screen where you disable vats in the vcm on your 2004..

http://i1050.photobucket.com/albums/...toWiz/vats.png

you'd just disable it here and the car will start and run. Now if your starter control is run through your bcm then that is an additional security feature but has nothing to do with that ls engine or it's ecu outside of that car.

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Thanks for the reply!

Maybe I rambled a bit much in my previous post. I understand that HPT doesn't communicate with other modules in the car other than the PCM for my specific setup. I also realize that swapped cars don't use the BCM or PIM. Yes, that is where my VATS is disabled in my tune currently as noted above.

I guess what I am asking about...

(Question 2) Which "handshake" does disabling VATS remove? Just the handshake with the BCM?

The necessary wiring to completely remove the BCM and PIM seems very straight forward, but I just wanted to make sure I wasn't over simplifying it.

99% sure it'll be a grey/blue stripe wire thats on the pim. this provides the earth to the relay once the bcm/pim agree on security. the other end of the circuit is a grey wire which goes to the starter relay. both of these wires come/go from your auto's neutral/park safety switch. Along with vats turned off the car will turn over.

I've just done another stripped down setup in 1 of my drag cars which utilizes a bcm/pim combo for a factory dash so i know this works.