Please Help..Backup Sensors again
 

So i took my car to the dealership to get teh mirror replaced and to explain to them what i was talking about with the sensors because they couldn't understand. And here it is for all of you: When i take my car out of park and put it onto reverse or go stright to drive, the backup sensors go of and chime 4 times. According to the book and ownign the car for 5 years, this is not normal. the mechanics could not figure it out at all(not like they did much but check the codes). I am taking it back tomorrow to get another mirroe put in since the one that they got doesnt look rigth either. Any suggestions or more backup of my arguement that tere is somethign wrong..

no damage or dirt built up

thank you

finally figured it out. the storage bin under the 3rd row seat was open... the absolute last thing i would of checked