Moving from 1227747 What is the best TBI ECM to use?

**dave w** · 01-22-2022

My choice for programming EFI Chips is the BX32P https://www.newark.com/batronix/bx32...batronix+bx32p

My choice for Erasing EFI Chips is the LER-121A https://www.newark.com/leap-electron...4?ost=ler-121a

I admit, my chip programming and erasing choices are not budget friendly.

I've yet to find an EFI chip the BX32 won't program. The BX32 has a chip identify feature too. I use the LER-121A to erase memcal chips too.

dave w

**In-Tech** · 01-24-2022

Thanks for the files. hehe, you wouldn't believe the hodgepaws of adapters I have had to fudge together over the years. Good job :)

**ScottP** · 01-25-2022

The old timers probably all know this, but for those new to working with the 95 and earlier TBI and TPI
ECMs/PCMs/TCMs, Moates has a really nice selection of adapters and tools.

http://www.moates.net/hdr1-memcal-he....html?cPath=64

http://www.moates.net/gm-19851995-c-64.html

-Scott

**1project2many** · 01-25-2022

Originally Posted by kilohertz

I was looking here... http://www.gearhead-efi.com/gearhead-efi/bin/

I will post them in the 7427 section as you mentioned. I just need to lift the lid and see what type of adapter I need to make, I should have the parts here to do it. I'll post when I get it figured out.

Cheers

That link opens a copy of the old .bin file library from the GMECM mailing list. I forgot we even had a copy of that.

**kilohertz** · 01-28-2022

Today I scored my 95 harness and another 7427 computer, plus most of the sensors, and I have a few questions.It was a long day of trying to carefully pull out the harness, and by the time I was getting it close to getting it out I was running out of light and I couldn't get to the back of the passenger side of the engine to get the O2 plug so I just cut the wires, and on the drivers side of the engine, just cut all the wires in the big bundle which go out from the engine harness back to the connector below the master cylinder. When I got home and washed up and recouped, I noticed that there was no fuel pump relay on the firewall and the big plug was missing from the harness, also no knock sensor plug. Is the fuel pump relay and plug somewhere else on these 95 C-1500? And where is the knock sensor? Maybe when I cut the O2 wires I also cut the knock sensor wire?? I can't seem to find any info on the second gen TBI harness removal process here so forgive me if this has been covered somewhere. I may have to go back tomorrow to get the things I missed??Thanks!

**kilohertz** · 01-28-2022

OK well my wrist has stopped bleeding and I had a chance to do some researching, and found the fuel pump relay is in the fuse box by the MC, and the knock sensor is by the starter, no wonder I couldn't find it or the plug, must have severed it in the little bundle going down the back of the engine on the pass side.

Going to start dismantling the harness tomorrow and clean all the dirt off everything. It was a very clean all original 95 and I also got the dist, coil and TBI. They are planing to crush it next week, I got there just in time.

Cheers

**tayto** · 01-28-2022

i don't know why you need the harness unless you are planning on running a 4l60e or 4l80e behind that flathead. you can repin the ecu plugs to the newer pcm style on your exisiting harness. there's also a few small wiring changes like bypassing the external knock module, as that is internal on the 7427.

EDIT: as for the fuel pump relay, 1995 was last year of tbi and first year of the newer style dash on the gmt400 platform. IIRC there was a big underhood fuse panel/relay box. it would not be my first choice in harnesses for modifying, 94 and earlier has the fuel pump relay mounted on the firewall.

EDIT 2: the knock sensor is on the passenger side by the starter. the wiring is usually with the starter wires, so unless you unplugged them you probably cut it. 7427 DOES NOT use an external knock filter. It is in the CALPACK. i would find a 7427 (with calpack) from a V6 with tbi to match your 6 cylinder flathead

**kilohertz** · 01-28-2022

Originally Posted by tayto

i don't know why you need the harness unless you are planning on running a 4l60e or 4l80e behind that flathead. you can repin the ecu plugs to the newer pcm style on your exisiting harness. there's also a few small wiring changes like bypassing the external knock module, as that is internal on the 7427.

EDIT: as for the fuel pump relay, 1995 was last year of tbi and first year of the newer style dash on the gmt400 platform. IIRC there was a big underhood fuse panel/relay box. it would not be my first choice in harnesses for modifying, 94 and earlier has the fuel pump relay mounted on the firewall.

EDIT 2: the knock sensor is on the passenger side by the starter. the wiring is usually with the starter wires, so unless you unplugged them you probably cut it. 7427 DOES NOT use an external knock filter. It is in the CALPACK. i would find a 7427 (with calpack) from a V6 with tbi to match your 6 cylinder flathead

Hi Taylor,

You're confusing my 2 builds, this thread is about my upcoming '68 Firebird TBI swap so I am gathering parts for a completely new setup. I thought rather than mucking around with a 747 harness pin swapping etc. I would just start with the correct red/blue plug harness, which is what I have done.

Thanks for confirming the fuel pump relay location, it's not a problem to add the relay somewhere else on the Firebird. I will go back and find the knock sensor and plug as I want to use it for the Bird.

Thanks!

Cheers

**tayto** · 01-28-2022

Originally Posted by stew86MCSS396

Dont see how that can be the problem when the tcc worked as advertised with the original ECM.

ya my bad... you can use your extra 747 and get the fuel pump relay plug and whatnot.

**trlrider** · 01-30-2022

Originally Posted by kilohertz

Thanks guys, appreciate all the info and advice.

Were the 7427 only available in '94-95 trucks/vans? Are there any tell tales signs for the vehicle to indicate it has this ECM as opposed to other ECMs from the same dates? Saves pulling a lot of glove boxes off the hinges.

i.e. VIN codes or glove box VIN stickers.

Also, while I have your ear, in the 7747, does the BLM data get deleted when the battery is disconnected? How is it stored in the ECM? I have been removing the battery cable every time I change the PROM tune, not sure if that is detrimental or not. I suppose I could be extra careful putting in the chip and leave the battery connected if need be.

Thanks!

My 1993 Suburban at some time in it's life had a dealer replaced ECM, and it was a '7427, so I lucked out when I bought it, swapped in earlier crate engine and started tuning.

**kilohertz** · 01-30-2022

Originally Posted by trlrider

My 1993 Suburban at some time in it's life had a dealer replaced ECM, and it was a '7427, so I lucked out when I bought it, swapped in earlier crate engine and started tuning.

I lucked out too. The truck I stripped was built 10/95, which technically is a '96. I was very happy to find the 7427 and red/blue harness. Stripping of all the old loom tomorrow and get it ready for install this summer...bloody snow.

Cheers

**tayto** · 01-30-2022

the vin is more accurate for figuring out year vs the manufatured date

**trlrider** · 01-31-2022

Originally Posted by tayto

the vin is more accurate for figuring out year vs the manufatured date

eh? yes, the vin does tell what MODEL Year it was built for, it does not tell the manufacture date though normal decoding.
What does that have to do with what ECM it has?
I have a 1993 Model year that had a dealer replaced ECM, that just so happened to be a '7427. I even found a late model year '92 with a '7427 at the salvage yard.
GM does supersede ECM's for various reasons, so it is not all that unusual to find one in anything from '92 to early '96 depending on the vehicle model.

**kilohertz** · 02-01-2022

This is too funny not to share...

I stripped down the new harness today and removed the superfluous wires, it's amazing how many wires are not needed. The whole harness was covered in oil so I washed it and wiped it all off, it should work just great in the '68 Firebird. When I was finished I sat down next to the workbench and had a beer, and casually looked over at the distributor cap and distributor that I got from the same truck....and noticed it only had 6 posts. WTF, I thought this was a V8 truck. Too funny, turns out it was a 4.3 C-1500 so I now have a good distributor for a transplant into my '66 Corvair, which I am also planning on a TBI install with dual small TBI bodies...one day. I hate getting old.

I'll read the MEMCAL in the morning and if it's something new, post it in the appropriate thread.

Cheers

**tayto** · 02-01-2022

Originally Posted by trlrider

eh? yes, the vin does tell what MODEL Year it was built for, it does not tell the manufacture date though normal decoding.
What does that have to do with what ECM it has?
I have a 1993 Model year that had a dealer replaced ECM, that just so happened to be a '7427. I even found a late model year '92 with a '7427 at the salvage yard.
GM does supersede ECM's for various reasons, so it is not all that unusual to find one in anything from '92 to early '96 depending on the vehicle model.

'96 is when the c/k trucks went to vortec, completely different induction system, harness and PCM. 1993 I could see getting a 7427 considering it used the same connectors. i am having a hard time believing the '92 was "dealer swapped" to a 7427. surely there would be some gm literature for techs to back this up. kinda thinking it's more likely someone swapped a door from a 92. did you verify the vin in the door matched the VIN on the dash? While on this topic, i have read that mexico ran TBI up until 1998 or maybe even 2000. being in texas it could be very likely you have these truc,. But being in canada very unlikely.

Also, not sure how much you've done in the automotive industry, but VIN number is by far asked for more to identify a vehicle than the date in the door. Have you ever gone to the ANY dealer for parts before? they usually want your VIN number.