My son and I have swapped the original 4.8 Vortec to a used 5.3 GM crate with ~100,000 miles. Do I need to order a brand new PCM/ECM VIN programmed and updated from Flagship One or can I have my old unit tuned? Pardon if I'm using the incorrect terminology but we decided to use this project as father and son.



If I purchase a new unit, will I need to have it tuned? Basically what are the next steps I should take from the electrical side as all other mechanical parts have been finished.



Thank you all.

 

You can have the Original one tuned to match the new engine.

 

The 4.8 and 5.3 are identical from the electrical (ignition/wiring, sensors, etc.) perspective. Literally yank out your 4.8 and drop in the 5.3 and everything will match.

Regarding the tune, I would recommend a place that specializes in GM trucks, if at all possible.

My Flagship One experience from a few years ago: I ordered an ECU VIN programmed for our 2013 T&C minivan that I had diagnosed as not commanding the alternator to charge. The new Flagship ECU threw a bunch of codes and the gas pedal didn't work. I chased my tail for several weeks, thinking maybe I had to do a relearn or something. I eventually reinstalled my original ECU and everything was perfect, minus that charge issue. I reached out to Flagship One and they had me "warranty" the ECU (forms ask what I did for diagnostics), which wasn't the end of the world, just was aggravating and set me back in time. The replacement ECU was good and it's been working fine. I later discovered their reviews are hit/miss...

 

Just get the PCM tuned from a reputable tuner.

My experience with Flagship one was good except the instructions to reprogram the key (push start 2011 Cadillac SRX) did not work. Ended up having to go to the dealer to program the key.