After replacing the left engine Gearbox Fire/Overheat Loop on a B777-200 aircraft; a Mechanic was informed the aircraft returned to the airport.

Narrative

I was assigned to work a B777-200 aircraft with a left engine gearbox fire/overheat loop issue. Myself and Mechanic Y were working together; he did the left side half I did the right side. I installed the loop on the engine with several Adel-[type] mount clamps; loosely; to leave movement for adjustment. I made the connections on the forward end of the loop with difficulty due to limited access and small hardware. While installing the rest of the loop frame mount clamps; one clamp proved to be very troublesome; I moved to the aft terminal connections while my partner worked on the problem clamp. I installed the rest of the mount clamps and checked the terminal connections. Then we closed the cowling; did the Fire/Overheat Test which passed; and ran the engine for five minutes with still no faults or messages. I can see how I had not correctly tightened the small terminals screws in fear of snapping them off. And also missed loop frame mounts due to frustrations with various areas of the installation. The [Maintenance] Manual (M/M) did not list [direct Mechanic] to remove the bug or the starter; if they were removed it would have made the procedure easier.