Pulsar can deactivate the AFM/DFM for you. It does a couple of other things too. I just refuse to pay 500 USD for something so simple.
So do the redneck broke guy paying for a truck thing. Yes that is derogatory but accurate.
1. Get a start stop eliminator. Worth the money, easy to install and will relieve you of hitting the button each time. About $100 or so, less with black Friday coming up. The auto start/stop or A.S.S. is nothing to play with.
2. Put your truck in L9. Run the shift lever past D and it shows L1, then use the plus button on the shift lever to show you L9. You will not activate DFM due to programing that is already in your PCM/TCM.
3. Change your oil every 5,000 miles. GM is asking your lifters to work both mechanically and hydraulically. You need fresh oil for that. Even the best and greatest oil (you fill in the blank) needs to be changed no later than 5,000 miles. Even shorter OCI if you short trip or idle the truck for extended times.
4. Also as critical as the OCI, use 91-93 octane. The variable timing component will advance your timing, keeping it from the bottom or most retard timing setting. This will relieve stress on other components. Live data on the engine supports this finding.
Or, don't do it. There are a lot of GM 5.3 and 6.2 trucks out there that don't have the problems we experience with engine issues. This is simply a preventative measure that most trucks will benefit from. That last statement is entirely my own opinion (but more than an educated guess).