I still don't know whether this is a 31A or not, but if it is there are two temp sensors associated with bleed air: one for the bleed air duct and one that senses temps in the pylon. When you say "fire loop," I think of the fire loops inside the engine nacelles for detecting engine fires. I would imagine that this is a common configuration on the Lear business jets (admittedly a shot-in-the-dark guess).
