I guess I wasn't very clear.
In normal operation if I come up behind another car a I get a message to the effect that a lane change to a faster lane is about to be made, the blinker comes on and, if the faster lane is clear, we move over to that lane. At other times under what seems to be identical circumstances when coming up on slower traffic it just slows down to prevent rear ending the car in front. No lane change takes place.
When clear of the slower traffic under normal circumstances the annuciator will announce that it is going to leave the passing lane, the blinker comes on and the change is executed. But sometimes that never happens and if faster still traffic is approaching it is necessary to manually operate the turn signal to effect the transition back to the right hand lane.