I put a pioneer stereo in my 2011 hhr It worked fine for 8 months then lost am/fm reception . I replaced it with a kenwood and have the same issue. The installer told me the interface bad so I replaced it and have the same problem . The antenna works fine when hooked up to a stereo not wired to the car but not with the installed radio. I also hook up a universal antenna to the installed stereo and it worked fine. Any ideas on where to look for the problem?

 

I moved your post to a new thread. That other thread was about bad speakers.

 

You probably didn't hook the pink wire up between the HU and the antenna. The antenna is amplified power comes from the pink wire. The pink wire is also the "on" signal for an amp.

 

I hooked up the factory stereo again and same problem. Could it be the bcm? Also no amp or power antenna.

 

The stock antenna is amplified; if it has no power it does not work.

Why in the world would you think "BCM"?

 

Cmon Don. You know it's always the BCM that's the fault.

 

Maybe I'm not being clear; here is my logic: antenna does not work when plugged into radio in car antenna does work with radio not installed. The antenna amp must be good if it works at all and is getting power from harness on radio not installed must be a problem with pink wire on the harness.
I don't know what the "interface" has to do with the antenna, unless the pink wire is missing or not making good contact. Maybe check for voltage on the pink wire?