the problem started with my car not starting when it was extremely hot outside and it sat in the sun i was told it was the main relay then a couple days later my cars d4 light stays light and it will not disengage from park and i get a buzzing sound from under the dash near the main relay if anyone could tell me what i need to replace or how to fix the problem is it the tcu and the main relay or something else?

 

Sounds like different issues, maybe, and need help understanding.
Has any work been done on the car, main relay replaced or are you waiting to be sure it needs replacing.
When cool the car will start (?) but the D4 light stays on and the car will not come out of park? Does the horn work, are the fuses good. Are there any stored codes (ECM or TCU).
Assuming it is a 4 cyl, fuel inj, auto trans.

 

A quick test for the main relay is to turn the key to the II position and do not try to start the car. Listen for the fuel pump to prime for ~2 seconds in the middle of the clicks. It should be a faint buzzing/whirling sound that comes from the back seat, so listen carefully. If you do not hear that when the car is not starting, then suspect a MFR problem or possibly a fuel pump problem.

As for the car not coming out of park, do your brake lights work when you push the brake pedal?

 

No work has been done to my car trying to figure out what's wrong before I dump money into it it will start when cold and I hear the fuel pump prime also my tail lights work and horn fuses are fine its an automatic 4cylinder love the car bought it for 400 and this is the first problem I've had with it beside a distribtor

 

pop the console around the gear changer and there is a solenoid that locks you in park. This happened to my cb7 also I just removed the solenoid and called it a day.

You can use your key to get it out of park can't you?...

 

You can remove the interlock switch, just PLEASE be careful. This will mean it will shift out of park without having to press the brake.