Gear shift locking

I have a 98 Honda accord v6 with automatic transmission. I have recently got into the problem of Gera shift locking and I have to insert key & release every time I want to start the car. Then as long as engine is running, car runs ok. D4 on display panel keeps flashing. Check engine light remains on. Many times all lights and monitoring goes off- not dispalying speed, odometer, fuel, engine temp gauge and no other indications except when i give side signal which works and headlights also work fine.
I first got check engine sign before @ 3 months. Got checked. It said Trans problem. Took to trans repair shop. Told Gear sensor bad, got replaced. Check engine light again after @ 3-4 weeks. Took to shop again. Was told Gear sensor reqd. some setting. I don't know what is that but they made check engine light disappear. Came again after a week or so. Not satisfied with response and service of first shop, took to another. Told tran oil needed to be changed. Got it done. After @ a month stuck with above problem now. Car runs good otherwise. No abnormal noise. Please guide with probable cause/trouble.

Ok, assuming it's the same code everytime, and the fact that the gauge cluster doesn't work, I'm fairly certain in saying that it is an electrical problem, and things like changing fluid aren't going to help. I don't know much about the inner electrical details of accords, but I wonder if it isn't a problem in either the gauge cluster, or the computer (or related grounds). My only other thought is that the other shop messsed up and it isn't the right sensor they put back in. Something along those lines wouldn't surprise me.