Passenger door open is being displayed even though the door is fully closed and locked. This means that the car cannot be locked can you advise as to where the sensor is Thanks
The exact year and model of your C5 would help us to give you better advice. However, the switch in question will be attached to the door lock mechanism inside the door. You will need to take the door card off to access this and fit a replacement part.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.