Wondering if anyone can help with this. I have been searching here and on google but haven't found much. I just bought a 2015 Expedition EL Platinum and get the message "check rear park aid". I also noticed that there are no gridlines on the display for the backup camera and the zoom button doesn't do anything. I don't know if these are all related or not. It appears the dealer or someone replaced 1 of the sensors as it isn't paint matched. But no clue beyond that. Thank you for the help.