Have you taken the top off and looked inside the coupler? You might find the problem easier than you think. If it is a capacitor, it will be very evident. The inductors seldom fail.
However, this sounds like a bad relay, and if it is, the insides will look discolored. It's a pain to replace them, but it can be done. Replacement parts can be ordered from Icom.
I have a schematic of the unit, but it is a VERY large jpeg and you'll need Photoshop or similar program to open it. The file is 1 Mb.