ECM to PCM upgrade

[Bill usn-1]

Decided to knock the dust off this old project!

Back in about 05 or 06 I worked with a few guys on thirdgen doing an upgrade from the old reliable ECM 8746/7747 to the later 95-95 TBI truck PCM. These are the same PCM I just used in the MPFI install. There are several versions used in TBI trucks and CPI trucks and vans with the 4.3. The main ones are the 8625 and the 7427. There are code difference in each application but all of them can interchange.

Back when I did this I was just looking at the latest hot thing. But at the time it just didn't seem worth it with all the ECM's avail and they still work perfectly fine on our old motors.
So I didn't feel it was worth doing a writeup at the time.

Well since I am using this PCM for the MPFI I figured I would show some of the versatility it has.

Back then I made this little crossover adapter so I can simply plug the new PCM into an existing ECM harness. This adapter isn't needed and actually takes more time to build then just swapping pins on the harness. But it does allow me to test ECM's, PCM's and chips in the same vehicle.

The big advantage and disadvantage to this PCM is amount of code it has. There are so many tweaks that can be done that just about any mod you want to perform, it can handle it.
Electric fans, wide band O2, turbo, electronic overdrive tranny....etc
As I get time I will be documenting most of these in my various project builds.

I'll also be adding all the pin changes required to swap this in.

So stay tuned as I progress through some of my projects.

First the adapter I made:





With the PCM plugged in.



Plugged into my old 72 TBI travelall.



Using Tunercat to log a little data and make a few changes.

[Julian 537]

Great thread Bill.

I look forward to hearing more about this.

[JeepsAndGuns]

I am having a hard enough time with the simple ecm I have now to worry about doing any swaps to a more complatated one such as this one, BUT just for the sake of pure conversation, I have a few questions.

You say it can controll cooling fans? I was just thinking the other day about electric cooling fans and was wondering if the 7747 could be used to turn one on and off at specific temps. I didnt see anything on the wiring diagrams for the 7747 for it, so I assume not.
Then you say this one can use wideband O2 sensors? So if one was to want to install one, then you wouldnt need to buy a seperate WB O2 controller like you would if you were to stay with the 7747 type ecm's?
Does tuner pro support these, and is the programming actually more complacated, or is there just more stuff in there you can change

[Bill usn-1]

The 7747 can't control fans or as you said, it would be in the FAQ's.

The pcm does have about 4X the code. So if learning 4X more is not more complicated then nope, it's all the same.


Yes tunerpro does support all these but as with the learning curve, you either need to learn how to write the definition file for data logging with tunerpro to read the WB or you need to hope someone else did it before you and was nice enough to post it publically.

The actual pcm code has to be changed to make the pcm operate them. most are well documented online but you need to have a small understanding of the hexadecimal addresses to write the new code into the old bin.

I'll cover most as I get to them.

[JeepsAndGuns]

Originally Posted by Bill usn-1

Yes tunerpro does support all these but as with the learning curve, you either need to learn how to write the definition file for data logging with tunerpro to read the WB or you need to hope someone else did it before you and was nice enough to post it publically.

The actual pcm code has to be changed to make the pcm operate them. most are well documented online but you need to have a small understanding of the hexadecimal addresses to write the new code into the old bin.

I'll cover most as I get to them.

I will definately be keeping a eye on this. I dont care anything about auto trans controll, but the possiability of using a WB O2 and being able to controll cooling fans seems like cool features.
I was at the local pull a part looking for some other parts and like I am, I take closer looks at every chevy/gm trucks and vans looking for spare parts or complete good harnesses, so far they have all been hacked real bad by other people. But I did find a 93 astro van with the 16168625 ecm. And since they are cheap there, I just went ahead and picked it up to toss in the back of the parts room as a WAY down the road future project. The harness had already been hacked under the hood, so I saved the plugs for the pcm and about 6-8 inches of the wires.
These are definatley diffrent beasts. I did a little looking and reading about them on moates. From what I looked at mine and read online, it appears the limp home chips are not removeable from the memcal, and the one I have is a V6 (BFMY) So I probably should have just left it and looked for a V8 one. But oh well, it was cheap. Are you running moates G1 adapter?

[Bill usn-1]

You can adapt any of them to work. Just set the cyl count.
Limp home can be modified for MPFI(see the MPFI version 1 thread).
I am running a moates adapter right now but you can also just cut the original chip right off and solder a standard 28 pin socket on. then you can drop a 27sf512 right in.
Or plug a zif socket into the 28pin socket if you prefer.
It's all pretty straight forward.

The MPFI install write up that Gravedigger did is an 8625 V6 PFI ecm.

[JeepsAndGuns]

I searched and read your MPFI version 1 thread. Very interesting. Thats pretty neat you can simply soder in one jumper to convert it from V6 to V8. I know you could change the bin, but didnt know you could do that to the limp home chip. I figured it would be easyer to start with a V8 bin than a V6 bin. But seeing how the eproms are sodered in place how would one read it to get a stock bin file that you could then tune? Or do you have to rely on finding one somewhere online to download?

That PCM I pulled, I can not remember what injection it had. I just glanced at the engine, but didnt pay any attention to it. So I dont know if it was TBI or port. Can you tell from the BCC? I dont have excell so I cant open your BCC lookup file. I tried to google it, but had no luck. Its BFMY.

[Bill usn-1]

BFMY=1993 astro van with 4.3(LB) man most LB's were TBI but it really doesn't matter since you will be removing or bypassing the stock chip anyways.

There are many bins avail in the file upload section of Moates. You could probably cut the chip off set it in the burner and read it.
If I had a specific bin I wanted that wasn't in the file section already then I probably would.
But most any you need are avail there.

You can use Open Office for a free look alike of MS Office.

There's been a couple guys copying all the bins and posting them on their own site but if they have them then they are avail. I have a couple links in the FAQ's.

The MPFI threads are in the FAQ's so no need to search.

[Jon In Tucson]

According to the BCC lookup file, your BCC is from a 1993 chevy with 4.3, manual trans and whatever ratio GU5 rear gears are...


BFMY 1993 34016 16192233 16168625 2234 2235 L1 LB4 4.3 MAN GU5


I haven't ironed out all the bugs in my own project, So I have great respect for anyone looking into the MPFI project. God Bless.
Jon In Tucson

[JeepsAndGuns]

Originally Posted by Jon In Tucson

I haven't ironed out all the bugs in my own project, So I have great respect for anyone looking into the MPFI project.

Exact same here. I am nowhere near doing anything like this right now, I am having enough trouble with the simple 7747 ecm system I have. I only bought this pcm just cause I found it and it was cheap. I have stuck it in the back of the parts room as a future project, for when I get way more educated on all things injection tuning. I will contune to watch and learn from bill and let him iron out most of the bugs as he goes along.