HOU-edge

Thank You for this forum! I recently purchased a 2011 Edge that has the reverse sensing system. I tried it the other day and it seemed to work fine. As i got closer and closer the beeping increased until it finally went constant. "Wow, I must be close" I thought. But when i looked i was about 3 feet away from the wall. Does anyone know if there is a way to calibrate that sensor system. I can do that good with the mirror. Thanks.