I completely reprogramed my ECM with the latest program from GM. I had no choice though because mine was from a newer model with the extra Solinoid in the valve body that mine didn't have. Did a complete relearn not just resetting the values. But it sounds like exactly how mine acted. The kicker is the wiring on these things do sometimes have issues so make sure you check that aswell especially up around the computer it sometimes rubs the harness and also down on the trans the connector pull it and it will get trans fluid in it causing issues. Also, check all your grounds rule out the simple things first. I did my grounds first because they had continuity BUT not great. Granted didn't fix it but don't hurt to make sure. Also check and make sure non of the pins are pushed back in the connector at the TCM this too can cause issues. Are you getting any codes? Do you have a good scanner to get the codes that do not set the Check engine light?