I am going to say water intrusion. Noting to base that on excpet the other day my realtively new PP that I installed last year went crazy after a hard rain that probaly got water on the dash. System was 'OFF' as fara as I knew. The display would not show any characters and just emitted a high pitched scream for about 2 minutes until I finally shut off the motor. When restarted the motor - all was fine. No problem since.