I've had this truck tuned by both PCMforLess, and now BlackBear, both great tuners for sure, I have nothing but great stuff to say about them , but I don't have tuning software, or the time for the learning curve to know how to use it properly, but I do know that the main thing that you have to do is flash in an 01-02 operating system, and make some adjustments that keep the battery light from flashing and whatnot. I'm sure that there has to be some info about this in the GM tuning section: https://www.performancetrucks.net/fo...cs-wiring-161/ , as this is old news, but still something that guys with 99 and 00 trucks run in to when they're new to the GM modding game or the truck has been a stocker all of these years and is now finally getting it's cherry broken

For my particular situation, I encountered this false KR problems years ago, before the tuning experts figured out a fix by just working with their lap top. I had to replace my 99 PCM with an 02 PCM (which I bought 2 of so I could always send one out to be updated while still driving my truck), I also had to get a newer model alternator (upgraded to a 145amp which I believe is for an 03 Denali), different belt to accommodate the alternator, replace the connector going into the alternator with a two wire connector, and run a wire from the alternator to the PCM...something to do with the PCM monitoring the alternator and/or duty cycling it I ran the truck for a while with just the 02 PCM and no alternator mods, and the battery light would blink slowly, non- stop. The alternator/wire to pcm cured the blinking batt light for me, but now the experts and well informed tuners know how to fix that issue with their tuning software. Unfortunately, it hasn't been in the cards for me to get into the tuning end of it yet, so I honestly have no idea what keys you have to hit I know for sure that there are folks on this site that definitely do know though