I have a 2009 F150 with the Sony sound system. I had to get the engine replaced, long story. Took it to the dealership where it sat for the better part of 6 weeks. I just got it back late Friday. I thought I would listen to some jams. However, I noticed I was not getting the usual bass. Played with the settings, checked fuses for Radio, Sync and Amp, all good. Checked connections of amp, everything checks out. Listened to the sub and it sounds like power to the sub but no music. I checked the internal connections of the sub and have the amp apart looking for any blown circuits. What am I missing? Any grounding in the engine block that I should look for that is specific to the audio system? Anything I can check that maybe the technician forgot to connect?

 

Have you checked the fuses?

 

I checked all the fuses that had anything to do with the head unit, amp and SYNC. None blown. I did the speaker test through the diagnostics setting (holding buttons 3 & 6), speakers were loud and solid. The sub, although it was audible, was very soft.

 

At this point, before digging any deeper, bring it to your Ford shop.