I was chasing a cold start issue. I was getting P0380 code and a clear indication of a glow plug problem. First I tried to replace the glow plug solenoid (or what I thought was the glow plug Solenoid) only to find out mine is one of the ones with the new solid state glow plug controller. So I replaced that hoping that that would solve my problem, It Didn't. Long story short the problem was my SCT tuner. When I returned the truck to stock, the problem went away. Then I pushed a different program in and it's still fine, but either I have a bad program or something went wrong loading it. I loaded my light towing program last May and only now is it cold enough to notice the glow plug problem. the moral of the story is when debugging a problem, return the truck to stock to eliminate the tuner.
Anyway, now to my question.
See the attached picture. The part marked by the square is my glow plug controller, but what is the part circled? Thanks!