I recently powered on my 2010 Prius and instead of starting up normal, it started beeping and on the dash there was the yellow/orange triangle with exclamation flashing, the overview of the shifter position had all letters flashing (p, r, n, d, b) simultaneously, and then on the right screen it read P LOCK MALFUNCTION WHILE PARKING, MOVE CAR TO A LEVEL SURFACE , DEPRESS THE EMERGENCY BRAKE PEDAL FIRMLY, AND PRESS THE P BUTTON TO TURN OFF CAR. Maybe not in these exact words but close. It is parked on the curb in front of my house on an uphill of about 20 degrees and has not moved in about 3 weeks now. Everytime I turn it on its the same thing. I can't get it to move and I even replaced the aux battery still same thing. I am about to have it towed to a dealer but am still trying to figure it out so I can save $1000.00 is what I am guessing they will charge me. I used an OBDII scanner today and a few codes came up. C1231 is one of them and I cant remember the other codes at the moment but I do remember that is said something about PEDAL POSITION SWITCH "A"/"B" MALFUNCTION and another one said HIGH COOLANT TEMPERATURE INPUT something. Any one have any HELP!!
Are you still on your original 12v auxiliary battery? If so, it's about that time to get a new one. That's probably your problem, lots of random and seemingly unrelated things happening at once.
I would push gently on the downhill part of the Prius - uphill to release tension on the park locking mechanism. That might allow it to release. ALWAYS use the parking brake, before putting the car in "P" or turning it off.
Put the Ebrake on fully, push the start button twice so you are in the ON mode, HOLD the shift lever to the left with your foot on the brake to put the transmission in neutral. Then push the start button and let us know if it starts.
!! Really? That's an extremely steep hill, like a 36% (or maybe 34%, depending on definition) grade. Do all those warnings appear before you try to shift out of "P," or only when you do?
You saved my nice person Dan! Middle of a blizzard and the park lock happened. I was stuck without this advice. Thank you!