4.3 to a 4.8 swap 2003 truck

[JASON11WS6]

I have a 2003 Silverado with a 4.3 and we're about to swap a 4.8 LS in it. Both are automatics/dbw. I picked up a wiring harness already from another 2003 LS truck.

Can I update the operating system with HP? Or does a dealer have to do that?

[JASON11WS6]

Really?

[dhoagland]

So long as both OS were available for your PCM from the factory

I did a Write Entire to a PCM and installed a 6.0 into a PCM that originally had a 5.3

I know there are also segment swap options too
I segment swapped a "Systems segment" into a 6.0 that was originally DBW and made it DBC

I believe segment swapping saves Credits. I'm pretty sure I had to license both PCM's when I went 5.3 to 6.0 Write entire (but its been a few years ago)

[DougO]

Yes you can update as long as the OS's match or segment swap and write entire

[Z06Luke]

If you have the P59 PCM (which I believe you do), then yes, that supports both 4.3 & V8 models available during that timeframe.

[Matt Vardaman]

Yes, you definitely can. My 2001 Silverado 5.3 (P01) is currently running the 2002 Tahoe 5.3 Flex fuel os .hpt file. I had to license the Silverado's tune file (which is 2 credits), Then downloaded the flex file and license that file (2 credits) when I flashed it(write entire) to my truck's pcm. It was already well tuned before, so I transfered the table data over to the Tahoe file.

In your situation, I would find a 2003 DBW 4.8 stock file in the repository and start with that. The 4.3 to ls swap information is out there.

[JASON11WS6]

Thanks guys, I'm gonna try the segment swap first. Hopefully it is as easy as that.