Warning Message/ Horn beep

I have a 2010 V with about 1000 miles on it. I have been intermittently getting a warning message that says Parking Malfunction...move to a level area and securely set parking brake. I can feel the parking "pawl" engage if the car is very slightly moving when I press the park button, but I don't the vehicle "knows" that has happened. The park selection does indicate selected on the dashboard display. I have found that message in the owners manual and will be bringing it to the dealer for repair. I have tried a variety of sequences for shutdown including pressing the park button prior to shutting it off, letting it self-select park by shutting it off motionless. Both of these have been tried with and without the parking brake being set with the pedal. It appears I may have a sensor issue in that the parking "lock" is engaging preventing the vehicle from rolling, but the car doesn't know it's happening.

I also have been getting a single horn beep a few seconds after the car has been shut off. It doesn't seem to matter if the above-mentioned intermittent warning is displayed or not. It happens all the time whether or not the doors are locked! It is the car horn, not the interior chime you hear when you lock the car. I don't know if the two issues are related. The car operates completely normally in all other respects. I have been unable to find any mention of the car horn beeping in the owner’s manual. Am I missing something? Predictions on the dealer response?

 

Well, I just returned from the dealer. I had their "Prius expert" mechanic look at the car while the message was still displayed. Because the issue has been intermittent, I wanted to be sure they could see for themselves when it was active. The mechanic let the car move slightly while pushing the parking button and the vehicle did stop immediately. It had moved perhaps a few inches and stopped like it does when you release your foot off the brake when parked on an inclined driveway. He had no explanation and scratched his head! He also hadn't a clue why the horn beeped each and every time the cars is turned off, even prior to locking it.

I guess most everyone on here is correct; dealers for Toyota are not the best. The mechanic asked me what year the vehicle was after he exited. If that's their Prius expert, and he couldn't tell after sitting in it and pushing the buttons, I am not so sure this is the dealer I want working on the car!