97civic4door

Hello, I have a 1997 civic Ex automatic. I had head gasket problems a few years ago so parked it. I just purchased a d15b from an importer around Atlanta.
Got the engine in and its running. However, when the car cranks up it revs to 3000 rpm and check engine light comes on. The car will also not allow it to shift out of park. I turn the car off, bypass shift lock, turn back on and shift into gears but the car will not pull. In every gear its the same, the no matter how much gas I give the car will only move on flat ground at a snails pace, and will not pull on any type of incline. Unfortunately I don't have a code scanner at the moment to read codes. Has anyone had a similar situation that may could shed some light on this problem. I emptied and replaced the fluid, but the problem is the same. I know the computer is designed to not allow the car in gear when there is a problem with the transmission, and also go into limp mode if it is in gear. Some people are telling me the clutch packs may be bad, but I would hate to get another transmission only to find it was something else the whole time. Any information would be appreciated. Thanks.