We tried everything we could with programming and nothing seemed to work. if I would let the pcm handle the fan lock up the fan rpms would never get more then about 800rpms and the engine would get hot towing. Manually lock it up to 100% and it would never get over 199deg. Not sure why we couldnt get a tune to work but customer needed his truck back and was cool with a fan switch to we through a switch on it and he picked it up. I am sure we will run into this again just have to get the programming right I am sure.