What could be setting off the front sensors on my Kia Carnival?

I have recently purchased a new Kia Carnival with a nudge bar fitted by the dealer. I recently washed the car in a carwash and now when I reverse and then put it into Drive the front sensors directly in the centre sound indicating that there is something there. It only occurs when reversing then shifting into Drive, not when going directly into drive from park. The only way to stop the alarm is to switch off the parking sensor manually near the gear stick. Help.