Rattle/vibration on/underneath axle area heat shield
After getting in my vehicle and starting it after the dealer "fixing" the P20EE issue (replaced the DEF filter), I noticed a syncopated vibrating sound at idle. Brought the diesel tech back to diagnose (engine cover, etc), we spent a couple of minutes trying to find it to no avail. I agreed to drive it home to see if would go away (dumb on my part), it didn't. Get home, think I've identified that either the heat shield over the axle area or whatever the heat shield covering is vibrating, positioned about the where the middle console is in the vehicle.
Going out on a limb, but does anyone know exactly what that heat shield covers? I believe the diesel mechanic had to remove it, along with the skid plates, to get at the DEF filter and I'm HOPING that's the cause of the sound.
Thoughts would be appreciated. Thanks.
EDIT: I'll add pics shortly.