Thanks so much for answering. I've tried it with the engine running, in reverse and varying distances behind the car, from about a foot to several feet and I still get no warning. Got any other ideas? Is it the same sensor that detects cars as detects people? I imagine it is. I don't think it's a cleaning issue if it's the same sensor.The back up warning signal will ONLY sound off when the engine is running and the shifter is in reverse
Depending on the location of the person, how fast they are walking and how fast your vehicle is moving the warning may or may not alert.
If the person is with in inches of the sensors they may not sound off either. You might play with this with a willing test person and your foot firmly on the service brake. Make sure that person is a couple of feet away from the sensors.