2000 Premiere Transmission

2000 Silhouette Premiere question for a transmission issue. On the highway between 65 and 70 mph, it suddenly drops speed and revs up close to 3200 on an inclined interstate and than drops back down to normal on the level highway. It showed lack of power and rev up multiple times. Check engine line flashes 12 times and went away.

I'm not sure what your problem is but if the check engine light came on then there should be a code stored in your ECM. Take it to a ASE certified technician and have him read the codes stored in your ECM. Hope this helps