The Check engine light on my 2006 Prius came on and I used my OBD reader to determine the code was P1121 - "Accelerator pedal position (APP) sensor - range/performance problem". I cleared the code to see if it would register again and a few weeks later same code showed up, but after driving it awhile the check engine light went out with out me clearing it and it remains off. The car drives normally with no other problems and when I monitor the APP sensor output I don't see anything particularly unusual. I can spend the $300 to have a new pedal installed, but I'm not sure there's problem especially if Toyota's design allows for a non-catastrophic failure mode.
My question is how does Toyota's engine control module manage a failure of the APP sensor? Is there a fail safe backup or is there potential for loss of throttle control like we heard about years ago in the news?