It's tricky , What I've found that works 70 % of the time , is start the vehicle , (with foot on BRAKE @ idle) put it in drive, then in reverse, shut the vehicle off then read, right as it stops reading the PCM , when it tells you that it's waiting 15sec. turn the key off then on, by that time the read function will tell you to cycle the key, do it........you'll know write(see what I did there) away if it's going to work.
I worked for an hour getting this one to read the TCM(see attached...BONE stock 04 1500 Ram GTX I just bought yesterday) , finally on the 6th try it worked.
I've also found that if the vehicle had been previously tuned with a Diablo CMR tune , you have a better chance of it being read, I've read 7 so far that have had a HemiFever Custom tune and all of them the TCM "read" on the 1st try...........and a Superchips tune is a 50/50 1st time read.
7250BASE(GTX).hpt