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Can you explain to me in a little more detail what exactly is going on? When you have your foot on the brake and push the start button are you getting a READY indication on the instrument panel? What color is the little light in the start button and is flashing at all? If you turn the headlights on are they fully illuminated and all the rest the interior lights fully bright?
This is what I suspected. What is happening is the 12 V battery is either or very low or going bad. When you power down the vehicle there is not sufficient power to drive the Park mechanism motor. The computer doesn't see this action and thinks the transmission is not in Park. It by default shuts the system down. You have a couple of options. The first one is to remove the negative battery cable to clear the codes. This advice that was given to you was fairly accurate. It does not reset the system it just merely clears the code in the computer and it starts out fresh. If you have a small trickle charger I would recommend putting this on the battery to see if you can bring the battery back to life. This battery probably is still covered under some type of warranty depending on your mileage. Once the code is cleared you could probably have a jump start if you don't have a trickle charger to at least get the engine running so that the code was cleared and the battery will charge itself as the car is left on. As long as the P malfunction screen or parking malfunction is detected in the computer you will have a difficult time getting it out of Park. Let me know if this resolves your problem or if you have any other questions regarding this matter.
This is a fairly common problem and malfunction on the warning screen and 90% of the time is related to a low state of charge on the 12 V battery. It is not likely that you have anything serious going on here.Skyvisions