2013 honda accord adding a sub

Hello all, I have a 2013 Honda Accord coupe someone has wired an amplifier and 2 12" subs in using a PAC SNI-15. Everything plays fine until all the doors are closed. Once the dome light powers down there is feedback coming through the subs. I went through the install and the SNI-15 is wired to the left rear speaker using the yellow and brown wires. I have changed the SNI-15 with another as well as changed the RCAs and moved the ground wire. If anyone has any ideas on what else I could try I would really appreciate it. Thanks

Do you have the 2 brown wires on the SNI-15 grounded?

I tried it with them grounded and without them grounded. I also tried using the front speakers instead of the rear speakers but got the same result. What the speakers are doing is humming really loud when the dome light turns off.

If you open the trunk, does this still happen? Are there any microphones in the headliner? One in the front and one in the rear? If so, they may need to be disconnected. If the car has bluetooth, there are going to be 2 microphones in the front of the vehicle. One is for the bluetooth, and the other needs to be disconnected. The front ones are in the overhead console by the mirror. I have not seen a 13 yet. But that is where it is in the 08 to 12. If it does not have the problem with the trunk open, tag the front speakers instead of the rear speakers. A guaranteed fix for your problem.

Yes it does.

Yes to which question? What are the answers to the other 2 questions?

I will have to check if the car has Bluetooth I did try tagging the front speakers also but had the same result.

It is the microphones. One in the headliner in the rear of the car, and one in the front. They both need to be disconnected.

OK sounds good do they disconnect at the overhead console or somewhere else?

Find the microphones and disconnect them. Usually behind a perforated grill. They should just unplug.