So I take it it's got an automatic transmission. Do you know if the gauge cluster was changed?
I had something like that happen to me when I swapped my gauge cluster that didn't have a tach out, and put one with the tach in. Check Engine light would go on when I opened the door, Oil light would go on when I pulled the handbrake, and all kinds of weird stuff happened. Basically, I took my old gauge cluster, turned it upside down and traced the lines on the back of it and noted where each one went. Then did the same with my new gauge cluster, and found out it's not the same. So I had to play with wires.
If you want to see how I did it, go to
http://public.carnet.hr/~kpuljic/honda/new_cluster/
That might give you an idea what to try next...