Possibly its all clock work.

Multiplex inputs are the door lock switches lock and unlock, door cylinder position switches lock or unlock, key in ignition switch, drivers door lock actuator inputs, door open switches and if you have it key less entry inputs. The only outputs are the door lock actuators.

If one think fails thy all fall. If you want to see what I see go to www.hondatech.info and see if you can find a etm for your car.

Some simple test you can do

For the door lock switches, Hit lock thy should lock hit unlock thy should unlock.
For the door cylinder position switches use your key on the out side, lock the doors thy should all lock. Unlock the door the first time it should just unlock that door the second time it should unlock all of them.
Key in ignition switch put you key in and open the drivers door it should chime at you.
Door open switches have your key on open all the doors see if you door open lights are all lit.
Key less entry hit un lock once the drivers door should un lock hit it again all door should un lock. Hit lock all the doors should lock.
For the drivers door lock actuator inputs you will need a volt meter and some free time.

Not as simple as you had hoped but with some time you should be able to get it. The multiplex is in you drivers door its a little box at the bottom.