OK. I just bought a 2010 HHR last week. It had the basic sound package, no onstar, so the next day I had the door speakers replaced all the way around. Yersterday/today I've installed my headunit with the GMOS lan 03 and an Infinity basslink sub. everything was dandy until I started testing. Everything work except for my rear door speakers. Everything seems to be connected properly afaik, but neither rear speaker is working. Any help is appreciated.