Ok so I'm trying to help a friend out she has a 2007 si sedan and found out it has a 2009 head unit. Since she has owned the car the sound system hasn't worked at all. Someone told her it was the amp so the amp was replaced today. I'm not familiar with these models that much but even though it's still a 8th gen head unit would it still work? The only thing I can think of without actually looking through the car yet is that when the previous owner put the 09 HU in he didn't connect wires or something came loose. Any help is much appreciated

The head unit gets power and turns on but no sound

 

Im dealing with a similar problem myself.. My Fiance just bought her first honda, an 07 DXG, and no sound to the front speakers. But the rear speakers are fine...

 

if balance is centered, speakers could be blown or missing all together. take off trim panel and connect a different speaker to see if you get sound.

 

OP can you try and take the HU out and double checking the connections and then give it a try. Let's try and rule out the first problem which is if it was properly installed!