Silverado ECM Swap - Using 2005 from a 5.3L 1500 on a 1999 5.3l 1500

Cloud909 · April 22, 2020

I am doing an engine swap. I originally had a 4.8l 1500 in my 1999 (new body style) Silverado. I purchased a 5.3l 1500 engine from a junkyard that was out of a 1999 Tahoe.

I have had the 5.3L engine rebuilt and would like to install it. I am sure that everything will mount up okay. So to try and keep this short, I want to install a 1999 5.3l 1500 engine, use the wiring harness from a 1999 (new body style) silverado, and use a 2005 5.3l ECM. I've heard some people say yes they will match up just fine (it looks like it will to me, but I haven't actually rebuilt it yet). I've heard others say there will be too many electrical issues. Please provide me with some definitive guidance. Do I need to look into reflashing my 4.8l ECM to run a 5.3l engine? Thank you so much.

kstruckcountry · April 22, 2020

It should be reflashed, but it is recommended to have the existing ECM tuned rather than swapping it out. I believe Black Bear and other tuners are quite used to doing this.

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SierraHD17 · April 22, 2020

Just use the original ecm... the 05 is a different generation and not worth using. Anybody with HP or EFI live can tune your original ecm.

Fun fact... your 5.3 will run well enough on the 4.8 tune you will probably think you don't need the tune at all.

When you guys are swapping engines in trucks like these especially V8 to V8 you don't need the harness and ecm... leave that for the guys doing actual LS swaps.

Cloud909 · April 22, 2020

I bought the AutoCal device, which I read uses EFI Live, from Black Bear Performance. Do you think that will be able to reflash it? I’ve been in contact with Black Bear but they’re slow to respond sometimes and it’s hard for me to get an answer from their tech. If I can do it myself I’m sure it would be faster.

SierraHD17 · April 22, 2020

Anyone that tunes with efi live (so not Blackbear) can send you a file to use your autocal.

Cloud909 · April 22, 2020

1 minute ago, SierraHD17 said:

Anyone that tunes with efi live (so not Blackbear) can send you a file to use your autocal.

I believe that Blackbear does tune with EFI Live, no? Is there a file online somewhere I can just download to perform the flash?

ohiohc · April 22, 2020

Not sure where you are but I have HP Tuners in Ohio.

SierraHD17 · April 23, 2020

On 4/22/2020 at 12:52 PM, Cloud909 said:

I believe that Blackbear does tune with EFI Live, no? Is there a file online somewhere I can just download to perform the flash?

No... because you have to pay to license that file which if the autocal allows sure but I don't think it does. Search efi live tuners.... don't lol.

Edited April 23, 2020 by SierraHD17

Cloud909 · April 23, 2020

Just now, SierraHD17 said:

No... because you have to pay to license that file which if the autocal allows sure but I don't think it does. Search efi live tuners.... don't lo.

I think you might be mistaken. Check out this link to their website. It seems to clearly indicate that their AutoCal device runs EFI Live : http://blackbearperformance.com/autocal.asp

I will read up on EFI Live tuners.

SierraHD17 · April 23, 2020

1 minute ago, Cloud909 said:

I think you might be mistaken. Check out this link to their website. It seems to clearly indicate that their AutoCal device runs EFI Live : http://blackbearperformance.com/autocal.asp

I will read up on EFI Live tuners.

I wasn't saying no blackbear doesnt... didn't even address that. I'm an efilive tuner lol... yes so is Blackbear. You commented how they are slow so try someone else.

Cloud909 · April 23, 2020

1 minute ago, SierraHD17 said:

I wasn't saying no blackbear doesnt... didn't even address that. I'm an efilive tuner lol... yes so is Blackbear. You commented how they are slow so try someone else.

Oh okay, I'm really sorry about that lol. How much would it cost for you to send me the file to use with my AutoCal device?

Cloud909 · April 23, 2020

Hello everyone, so I have made a mistake and just now noticed upon doing some VIN inspection more closely. The ECM I have is actually out of a 2000 GMC Sierra 1500 with a 5.3l engine. The engine I want to use it with is a 5.3l from a 1999 Silverado 1500. Will this work? I can start a new thread if someone thinks that would be more appropriate.

CamGTP · April 24, 2020

Yes, that is fine. There is hardly anything different about the two.

One major thing though is the injector settings. The 1999 trucks came with 21lb/hr injectors and 2000+ came with 25lb/hr injectors. I would suggest not using the 1999 injectors are they support basically zero power above factory.

You may want to double check the part number of the injectors you have. If the engine isn't going to be modded a lot, then the 25lb/hr will do just fine. Camshaft upgrades and things like that would likely need larger ones.