No volume after headunit swap?!?

[My3rdBaby]

Ok, this is driving me a little crazy. I just picked up a 91 240 coupe. It had some OLD crappy Kenwood in it, so I was going to put my pioneer cd player in from my 89 hatch. I did...and now there's no volume! The cd player is playing fine and shows to be working and putting out volume, but I can't hear anything! Not even static! I've checked and re-checked the wires and don't know what else to look for. Can anyone give me suggestions?

[My3rdBaby]

Well I figured out it's the "factory amp." I guess I'll try the amp bypass and see if that gives me the results I want!