Would like to get some transmission tuning in my van it is the duramax(lgh)/6l90.

Hptuners cannot read ecu, but reads tcm just fine. I was told by hptuners support that they have to be read together in order to tune.

They said to flash back to factory (I am running efilive ecu tuning), and then read both together. I have tried this and it does not work.

Anyone have some knowledge on this?

Thanks