Remote not working on automatic doors

I have a 2005 and my remote recently started acting up when I try to open the passenger side door.  It works after I press the button several times and if I''m close to the door.  I can use the switches inside to work both doors and the driver''s side is fine with the remote, so I don''t think it''s an issue with the battery.  Does annyone know where the sensor is located to make the remote work?  Possibility it''s dirty or blocked partially??  It''s an $80 minimum charge just to take it in then the charges to fix it.  Any help is appreciated.

I have a remote that was not working as well. I opened the remote and found that some of the electronics inside had been dislodged. Once I soldered them back in place everything worked ok.