Audio Systems: factory amp, buick regal, regal ls

Question
i have a 2001 buick regal LS with a factory amp and i want to put an after market amp in my car but i want to leave the factory amp in there to.
when i put the after market amp in the power LED will not come on but the protect LED does so how do i get both to work together or will they.thank you

Answer
I must know what you are going to do with the additional amp.  Can you explain that to me?

It is no problem having additional amps.  The input can be paralleled from the other amp. But the output must feed either new speakers or the same speakers that are already in the car (but if you do that, the old amp must be disconnected).  You cannot parallel the outputs of the two amps.

If I don't understand the question, please ask me further with your explanation.

Thank you,
Cleggsan