SJC: Clear security in Term B with a Term A boarding pass?
 

I'm returning a rental car to SJC early in the morning later this week for an AA flight in Terminal A. Does anyone know if I can clear TSA in Terminal B?

I'd rather just walk across the street than get on the shuttle and loop all the way around the airport....

Yes, absolutely, assuming you don't need to check any luggage and you already have a boarding pass.
You could also walk outside on the curb in front of the terminal if you'd prefer.

^^
Perfect, thanks! Yes, this will be carry-on only, and a mobile boarding pass.
I have done the outside walk before, but it is not the most pleasant experience, plus the Priority Pass lounge is in between Terminal B and the AA gates, so in addition to skipping the rental car shuttle, it will be nice not to have to double back to the lounge.

Terminal A and Terminal B are connected airside, and TSA couldn't care less if you're trying to clear security in the "wrong" terminal.
They're so close to each other that you'll barely notice that you're switching terminals.

I do this all the time, for the same reasons - it's the fastest path from the Rental car return to The Club at SJC.

Only catch is that depending on the time of day the line in terminal B always seems to be longer than that in terminal A - although if you've got priority then it's generally short in both. Term B does seem to get the dogs working more frequently than terminal A too, which can speed things up significantly (basically Pre-Check like security for everyone)

Interestingly my UA flight on Wednesday night actually arrived at gate 17, which is the first gate in terminal B (UA is normally in A). I'm not sure if they are actually using that gate or if it was just an exception.