When you send your computer off to have it reprogrammed, do they have some kind of special reading software, or do they just hook say, a laptop up to it and just change certain parameters?? If that is the case, do they have to install any new parts to the pcm or is it just strictly knowing what parameters to change??

 

check here, might answer some of your questions.

www.pcmforless.com

 

I know where to go to get it done...I am just curious about the procedures. He doesn't explain how he does it, just what he can do and for how much. I am more concerned with the process. Thanks for the reply though.

 

What they change will be dependent upon your needs and what you want changed.

No new PCM parts are used. It is all changing parameters within the code. To get into a detailed explaination would take time, however more than likely they use special software to change those parameters.

Why do you want to know?

 

they usually change things like timing advance, volumetric efficiency, WOT a/f ratios and other things depending upon what exactly youve done to the car.

this is accomplished using tunercat or LT1edit which is a program that allows you to manipulate a program for your needs and then reflash that program back into the PCM.... in a nutshell.

 

I do alot of programming at work and I was wondering how they did it b/c if you don't have to have some expensive reading tool...then I could just plug my personal laptop up to it using a terminal simulator and when the power is turned on then all of the computer's nvram would pop up and show all of the parameters and give you the ability to change them just as you would a Cisco router or something. If this was possible then I would get the pcm off of a wrecked 95 that I have and play around with the settings. This would be the same way the PCM for less guy said he got into doing it himself. Plus it would be alot cheaper. Does that make sense???

 

If you read PCM code it is just a Hexadecimal string. Unless you are able to dissasemble this, it is useless. Custom programs out there such as TunerCat or LT1 E allow you to read certain parameters within this code because they know where to go to find and change it. The code itself does not give "parameters" it give absolutely nothing for information.

If you are capable enough to COMPLETELY disassemble our PCM's, man, I am right there looking over your shoulder!!!!! There are parameters I really want to change but as of now, have no way of knowing where they are located within the hex file.

 

Ben,
What other parameters are you looking to change that aren't available in tunercat or LT1 Edit?

 

That's the answer I was looking for. Thanks. I work for Bellsouth installing switches for big hospitals, etc....alot of the error codes that we get on the switch are in hexadecimal format and we have to break it down and figure out what the error is, so I am familiar with hex...but it sounds like you are saying that if you don't know where to look then even though you can read hex it is still useles??

 

That's pretty much it.
I don't know of anywhere that you can get the broken down code.

 

LT1 E allows modification of "Knock count to enable KR" where Tunercat does not. Since I don't want to use LT1 E, I want to change my Tunercat. Anyone use LT1 E who is willing to send me a few changes to this constant?

Also, I have always had a desire to find where in the code the reference to the O2 sensors is. I always had a desire to mess with this. I assume it has to be part of the code that tells the computer to look for 450 mv.

I want to be able to modify the PCM so we don't have the "mystery" timing. Dan, what you showed in your program as a timing modifier was different than mine. I do not know if possibly our MAF's are connected here or not. I had to recalibrate mine and I don't know if you have had to. This I find interesting but makes for irritation when tuning.

Ben