1226026 - Crossfire

**NeilBreakwell** · 01-22-2019

Hi, Guys -
Just starting to learn about the fascinating world of GM ECMs ...

Have a 1983 Trans-Am with the 305 Crossfire engine.

ECM ID number is 1226026 and PROM has the following markings on a sticker:

DELCO
ASY
5597

Anyone know what the "PROM mask ID" is for this ECM/PROM ?

many thanks

**stew86MCSS396** · 01-23-2019

https://pcmhacking.net/ludis/c3xref.html#1226026

**1project2many** · 01-23-2019

Hello Neil,

I have some 6026 Crossfire calibrations but I do not believe I have definition files. I have never found them! The prom is OTP, One Time Programmin, so it cannot be reprogrammed. Many folks find the better option is to use a later 7747 or 7427. I opte to install the 7747 then moved up to the 7427.

**NeilBreakwell** · 01-23-2019

Thanks, guys ...

@stew86MCSS396 ...
Does the "program ID" in this link ($0F) refer to the PROM mask ID ?

@1project2many ...
forgive my ignorance, but what is the "7747" and "7427" that you refer to ?
alternative ECM numbers which are interchangable ?

best
- Neil

PS - appreciate that the PROM is one-time-programmable, but I'm guessing that I could replace with 2708, 2716 or 2732, which are all 24 pin DIL devices ?
May have to think about what to do with the chip enable lines though ?

**steveo** · 01-23-2019

i know its disappointing, but that's a horrible ecm to use for learning. in the 'fascinating world of GM ECMs' we would rip that thing out and replace it with something else. if you search this forum for 'crossfire' i'm sure you'll find other people that have done that.

nobody has really been able to (or spent the time on) reverse engineering those calibrations (maybe because the ECM isn't very good anyway), so you'd be working blind.

i've tuned other ancient ECMs that did have some research done on them already, and most of those early ECMs are primitive to the point of being useless for modified engines

even if you manage to find a way to tune it, your hard work wont give you the kind of control you're looking for. it probably has a 4x4 fueling table or something and most of the other math is hard-wired outside of the calibration. redneck tuning it with an adjustable fuel pressure regulator or a potentiometer on a map or temp sensor would probably give you similar results if you just want to bump fuel a bit.

...unless you're doing it 'because it hasn't been done', in which case i take all that back.

**steveo** · 01-23-2019

here are some bins that someone has pulled from 6026 ECMs...

http://www.gearhead-efi.com/gearhead-efi/bin/1226026/

**NeilBreakwell** · 01-23-2019

Thanks for the advice - it is much appreciated.

However, my goal is really to understand the ECM in my car down to the level of the firmware, rather than to tune or tweak it. So I guess I am doing it "because it hasn't been done" :)

So, the challenge is set - if I can figure out the PROM mapping for this ECM, I'll be sure and share it with the world :)