TBI harness swap?

Shtbox69 · Jun 1, 2019

Hi guys. I have a 94 C1500 4.3/auto and Im swapping in a 90 305/5spd(cause it was cheap) for my daily. Is my best plan to keep the 94 harness and ecm, and buy the right memcal? ,,, or can I swap in the 305 harness and ecm. Not sure it would work with my dash, ect
Thx in advance. Shtbox

Frank Compagnon · Jun 1, 2019

Use the V6 harness and change the chip, or if you can, get the computer (ECM) that comes with the engine, that way you don't have to replace the chip. It would use the same computer (ECM) harness plugs. Both, 94 and 90, would be located in behind the glove box.

PlayingWithTBI · Jun 1, 2019

The 1990 trucks came with a 700r4 (4l60) trans and ECM (probably 7747), the 1994s came with a 4l60E trans and PCM (probably 7427 or 6395) which also controls the trans. The 7747 has a baud rate of 160, 7427 was 8196 (I think), way faster and better control.

1990s came with a 12 pin OBD1 connector, 1994s may have come with a 16 pin OBD1 connector. 94 - 95 was a weird transition era for GMs controllers/communications.

Here's some other info including bin files and wiring diagrams

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

Shtbox69 · Jun 1, 2019

Thanks guys. Do you know if my 1990 chip is compatible with my 1994 ECM? As stated, I dont believe they are the same ECM, between years. I will check the service number on each.'90 Donor truck just got here today

PlayingWithTBI · Jun 2, 2019

Shtbox69 said:
Do you know if my 1990 chip is compatible with my 1994 ECM?

No it's not, the 90 chip is a 2732A (32K), the 94 is a 27C512 (64K).

https://xtronics.com/wiki/GM_ECU_eproms.html

Another way to go is the EBL FLASH-2 on your 7747 ECM, it can run a 5-speed manual and you can tune it yourself

https://www.dynamicefi.com/EBL_Flash.php

Shtbox69 · Jun 2, 2019

Thx. I think finding a used 94 V8/5spd ECM or chip, is what’s in the budget Thanks for getting back to me

Shtbox69 · Jul 8, 2019

PlayingWithTBI said:
No it's not, the 90 chip is a 2732A (32K), the 94 is a 27C512 (64K).

https://xtronics.com/wiki/GM_ECU_eproms.html

Another way to go is the EBL FLASH-2 on your 7747 ECM, it can run a 5-speed manual and you can tune it yourself

https://www.dynamicefi.com/EBL_Flash.php

I bought a used '94 V8/5spd ecm for my swap. I noticed the '90 305 donor has a est module on intake bracket, and 94 doesnt. Does this mean I will also need a '94 V8 distributor, for my oem harness to plug/play? Thx for the help

Shtbox69 · Jul 8, 2019

PlayingWithTBI said:
No it's not, the 90 chip is a 2732A (32K), the 94 is a 27C512 (64K).

https://xtronics.com/wiki/GM_ECU_eproms.html

Another way to go is the EBL FLASH-2 on your 7747 ECM, it can run a 5-speed manual and you can tune it yourself

https://www.dynamicefi.com/EBL_Flash.php

I bought a used '94 V8/5spd ecm for my swap. I noticed the '90 305 donor has a est module on intake bracket, and 94 doesnt. Does this mean I will also need a '94 V8 distributor, for my oem harness to plug/play? Thx for the help

TBI harness swap?

Shtbox69

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Frank Compagnon

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PlayingWithTBI

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Shtbox69

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