Just wanted to post here, in case some of you looking for this info.
My 2014 Outlander with dealer installed rear parking sensors started doing these double beeps ( beep, beep ... delay ,,, beep, beep) when I put the car in reverse indicating some kind of error. The system wouldn't work. It would just beep when in reverse
It took me a while to find the manual for the install kit
Double beep - single sensor bad
Triple beep - two sensors bad

I pulled out the sensor that was not clicking (when you put your ear to it) and it was all rusted inside.

Hope this helps ....

Install kit
MZ350334
Sensors rear
MZ350325AK (blue)


OEM parking sensors kit troubleshooting section