I have a 2005 Pontiac Sunfire 2.2 Automatic. My problem is the transmission shifts are hard and not smooth. I can disconnect the battery and everything resets back to normal, until the cooling fan kicks on. After that, it clunks going from Park to Drive, and the shift points harsh like having a shift kit installed. I have removed the cooling fan fuse and relay bypassing the fan, but did not change anything. I have also swapped out ECM’s, but still having the same issue. Hoping someone can help me with figuring this out. Any suggestions? Thanks.

Just a wild guess. Engine temp sensor?

After thoroughly investigating I found it to be an air intake temperature sensor. Thanks everyone for your help.