Have your car emptied of everything inside, out of manners alone the car should be clean. My sister failed hers because of dog hair and had to reschedule the test for another day. I took a look at hers before the test, told her about the smell of dogs from it but she never got the smell at all, didn't put in any fragrance or fabreze, but the car wasn't in any way dirty. I just wonder was it the smell that failed the test?