I swapped a 2008 GMC Sierra RCSB 2wd V6, but I'm having one last issue. I used a 2008 5.3 truck harness, a 2008 E38 ECM from another 5.3 truck, and a frankenstein engine - gen IV shortblock with gen III heads and intake. it all went together surprisingly easily, and after completing the security re-learn, I'm left with 3 codes:

Crank re-learn not performed
Fuel pump module lost comm
Fuel pump ckt malfuntion

The crank re-learn I was totally expecting. the other two codes seem to come from the fact that the V8 trucks had a FPCM, but the V6 trucks did not. Can I just delete/disable the FPCM from the tune and use a more "traditional" method like a ground or reference voltage signal to activate the fuel pump relay? I really don't want to put an FPCM, pressure sensor, and associated wiring in this thing, plus get a dealer reset.

Any help is appreciated. in the mean time, if anyone has questions about the swap, feel free to ask or PM me.

 

Hey man, i know this post is old but were you able to figure it out? Im having the same exact issue, same exact codes. Threw in a gen 4 motor with gen 3 heads just like you did but still having the same issues.

 

Anything on this i am running into the exact same problem would love to know the fix thanks in advance