I just did an fbody fan swap on my 01 Silverado. I am having the same issue with them being on low no matter what. It doesn't seem to matter what I set stuff too. I am using efi live. I keep reading about guys changing to a 02 OS system. Can somebody explain what I would need to do this? Also would I have to buy a new vin licence? Or if there is anything else that I need to check? I can control the fans correctly with efi live. The high fan kicks on when it reaches operating temperature. Just the lows are on only when the truck is running.