Here explain a short story first:

Yesterday after car battery changed then the car audio look like lock with the volume increase to maximum 80 then only can listen little bit sound. Minimum volume is 0 & normally i m use volume 26 only.

Then i ask the workshop what happened then they informed me change car battery not affect the car audio. The root cause of car audio not function is my car audio is cheap brand & closely spoil before change the car battery.

So want to ask is my car audio is a cheap brand? My car audio is Eclipse CD 5415.

Some expert know to unlock the car audio because i go to accessories shop then they ask me go back to Chevrolet to ask due to the car audio is originally installed in the car when bought the car.