newZman

I am considering an LT1 swap, I have an LT1 out of a 97 Camaro SS (suppose to be an SLP). I do not have the original key, just a wire harness and computer.

Was there some sort of pass-key feature on the 97 Camaros and if so what was it and how do I work with or around it?

I really want to put the LT1 in my 84 but not sure about the key thing.

Thanks a lot,

Terry

newZman

Maybe my question is mostly a stupid one...

I am thinking, now, that since I have an 84 Camaro with no passkey I dont have to worry about anything on the vehicle side as far as VATs goes.

Do I need to do anything with the ECM for the new motor, such as disabling in PROM?

Thanks for the help.

ASE doc

The 97 will have a EEPROM with "flash reprogram" capability, no removable PROM. The 97 had a vehicle security system that was part of the Body Control Module's domain. What the PCM(powertrain control module) from the 97 will need in order to work without the BCM is a reflash telling it to ignore the BCM or lack thereof. Or something of this general sort.

Post a thread on the "Engine Swap" forum asking this same question. Many have done the LT1 swap and someone there will have the exact answer to your question.

camaronewbie

And 97 has a VATS system just like the 3rd gen - so any usual VATS bypass module will disable the VATS - I used the resistor trick in my 1997 when the VATS went out on it.

But if you don't have the donor car's VATS module, you'll need one of those bypass units (about $50).

newZman

Thanks ASE doc and camaronewbie!
I'ld like to try and reprogram the ECM myself for this if I can figure it out, but if not I may have to do the bypass unit. Unless...

What type of signal is the fuel enable pin of the ECM (C1-pin25) looking for (i.e. high, low signal, clock)?

Anyone willing to put a DMM on that signal and see what it look like when the key is in the ignition turned to the ON position (shouldn't matter whether the car is running or not)?

ASE doc

Passkey 2 uses an 80Hz 5v on/off signal. The bypass modules can be configured to produce either one of the two different frequencies used by passkey 1 or passkey 2. On the 97, the VATS would have to be part of the BCM CAN, not the PCM.

ASE doc

I'm unable to find any definite information on the 97 right now. Experience tells me that the 97 was a Serial Data Bus car, using a Body Control Module. All body electrical functions(door locks, HVAC, security,etc) were managed by the BCM, not the PCM. The PCM managed the engine and transmission only. Since you are installing the LT1 and its PCM into the 84, you will not be using the BCM from the 97. Therefore, you will not be dealing with any of the BCM's periferrals, such as the Passlock module.

On the 97 the BCM receives the security enable signal from the immobilizer module and then sends an enable signal to the PCM. I've diagnosed many of these cars and I'm sure I remember seeing "key in" in BCM data. If I'm correct, only thing you need to concern yourself with is reprogramming the PCM to ignore the lack of BCM input. Again, i am unable to verify this right now. Post a thread on the "Engine Swap" forum to find out just what others have done. Alot of members run LT1s in their thirdgens.

newZman

Yes, according to the schematics I have the BCM make the determination whether the right key is in there then sends the "Fuel Enable Signal" to the PCM and the PCM turns on Fuel pump.

It sounds like the signal being sent is a clock. What is the frequency of the other signal? You said there are 2 different clocks used.

If I can figure out all the frequencies being used I can make a pulse generator for a couple bucks using a 555 timer and a few discrete components that should fool the computer. This way I would not have to reprogram anything.

Thanks again ASE doc.

ASE doc

I see your point. Generally, on the EEPROM systems, people just reprogram the PCM because it's reasonably easy and the equipment and software are becomming increasingly inexpensive and available. This also allows you infinite control over timing and fuel maps and every other function of the PCM(aren't computers cool?).

I'm not sure where you might find the signature of the BCM's enable signal to the PCM.

Another concern you would have would be code U0095(IIRC) which is "no communication from BCM". The PCM sends out a diagnostic pulse to the BCM, and on later models, to all of the modules a the UART bus, and watches for a response telling it that all modules are online and functioning. If any module doesn't respond, it sets a U code. Meaning there is a problem in the UART(Universal Asyncronous Real Time) Serial Data Network. I don't know that this code would cause you any drivability complaints but assuming that you want a fully functioning install, I would expect that you want to avoid such issues. The only way that I can think of for you to prevent these communication codes is to reprogram the PCM to ignore the missing BCM.

Or just use an aftermarket DFI system to run the LT1.

newZman

I definitely want it to work right. I want that check engine lamp to work as if nothing changed along with every other dash light. Bassically looking stock but with the goods.

This information puts a bit of a damper on things, it sounds like I need a BCM... Forgive my ignorance, but what is a DFI? And, do the bypass modules mentioned above take care of the missing BCM? Also, will reprogramming the PCM take care of the missing BCM?

newZman

I missed this I think my questions are answered here. Thanks ASE doc. I have the factory service manual for the engine and tranny for the 97 and up GMs, including all electrical schematics. I'ld be happy to look up anything you need.

ASE doc

Thanks! Have fun with that project and keep us posted.

camaronewbie

From what little knowledge I have on my 1997 Z28, that all sounds about right ASE Doc. I'm pretty sure you are correct with the BCM vs. PCM info. My 97 (as far as I know) has a BCM - I remember having some weird little issues trying to get a new (used) key fob "programmed" to the car (or visa versa) - I had to do all kinds of weird stuff with lock buttons and such to get the new fob to work right with the car (that's why I think it has a BCM like you stated).

Anyway, you guys are past my scope, so Good Luck!

ASE doc

Yeah, programming keys, or a replacement BCM or Passlock module is a long process. The TECH2 GM scan tool can bypass the process and perform a quick learn.

newZman

I have read about the tech scan tool in the GM manual but I didn't know you could buy one.

Is that something that can be purchased by anyone? is it a fortune (over $500)?

Thanks camronewbie and ASE doc.

ASE doc

You really need to talk with other LT1 swappers. The GM Tech2 is a very uesful tool for diagnosing OBDII GM vehicles. However, you're installing the LT1 into an early 3rd gen. Unless you plan to completely rewire the car to use the entire body and powertrain control system, with its serial data bus intact, the Tech2 will not be of any use to you. Go to the engine swap forum and ask others what they have done. There are several if not many who have done this swap. Some that I've seen have done stellar work in performing this swap and can tell you just what worked for them.

newZman

Thanks ASE doc, I did that not too long after you mentnioned it and have recieved a few responses here, if anyone is interested. https://www.thirdgen.org/forums/ltx-...oing-into.html

ASE doc

Looks like you received some good input from the swap forum. Be sure to post a thread on your own swap there for the benefit of others.

newZman

Yeah I got that going too here, for those who are interested https://www.thirdgen.org/forums/ltx-...84-ho-z28.html. I am mostly in the planning/prep stage at this point.

Thanks again.