The TSB investigation -- the first of three launched in the wake of the crash -- has found a switch on the ship's telegraph system malfunctioned, so the captain's call for full power forward was never relayed to the engine room.
Terrified passengers watched as the Coho crashed into a float plane dock in the Inner Harbour on the evening of July 10.
The ferry was reversing to leave the harbour for its sailing to Port Angeles when it collided with the dock.
The dock was heavily damaged, but the Coho was able to continue on with its journey.
The broken switch was replaced after the crash.
The results of U.S. Coast Guard and Transport Canada investigations are expected soon.