Rear park assist ultrasonic distance sensor errors - troubleshooting, disabling?

[Entrekin]

2012 sedan. For no apparent reason (no accident, impact, etc.) the rear park assist sensors have started throwing errors. Consistently alerts every time I start the car and when I slow down to below about 10 mph. Park Assist is turned off, but it makes no difference. I'm curious if anyone has tips to help troubleshoot what's causing this or a way to simply disable the alert, because I never use Park Assist. If the solution is to replace the sensor, how do I get to it? I'm not wild about paying dealer rates to fix something I don't use, but I'm also not a grease (or electron) monkey. If there are simple things I can try before calling on a professional, that's what I'm looking for. Thanks!

 

[Mcc]

I would clean them even if they look clean

 

[Entrekin]

Thanks for the suggestion! I've wiped them down, squirted with WD-40. Neither thing made a dent. However, posting about it here did - after going off for about a week, it hasn't made a peep since I posted. Go figure.