Back up lights not working all fuses are good and bulbs have been changed. on 2006 Chrysler PT Cruiser

I understand there is a switch or wire that is attached to transmission but the mechanic stated he did not see switch. Need detail on how to get lights working.

Asked by for the 2006 Chrysler PT Cruiser
the back up light sensor is incorp. with the trans range sensor on the side of trans