Anything can be done. My 99 with 4L60E had no tow/haul. I upgraded to a 0411 pcm from a Chevy express van and added a momentary ground push button switch to the appropriate wire on the pcm. I have no indicator light but tow haul works. I even modified it in EFI Live to lock up the TC in second at over a certain speed along with other shift points, etc in the tow haul trans section of the tune file.