1997 Pontiac Bonneville Bonneville stutters and shifts hard

My 1997 Bonneville back in Feb and it was below zero would not shift from od to lower gears like when you would stop at a stop sign and try to get up to speed. Now it is sifting hard and kind of stuttering when going up hills at 55 or so. I had a mechanic friend of mine hook it up to the computer and it is blowing a P1655 code which is evap emission purge sylinoid control circuit which in the book says something about shifting of the trans as well. I checked the fluid in the transmission and it smells like is burnt. But not real bad. I am wondering if it could be the trans sylinoid and also a new trans filter and flushing would fix? Please help! Thanks!