The parking aid system detects objects behind the vehicle when the vehicle is in reverse gear. The parking aid module does this by calculating the distance to an object by the use of 4 ultrasonic sensors mounted in the rear bumper. The ultrasonic field is emitted in a semicircular area around the rear of the vehicle. The parking aid sensors can detect objects approximately 1.8 m (5.9 ft.) to the rear of the vehicle, 50 cm (1.6 ft.) to the rear side of the vehicle, and 16 cm (6 in) above ground. A 750 Hz variable warning tone is generated from a parking aid speaker attached to the parking aid module. The parking aid speaker increases its warning tone rate as the vehicle gets closer to an obstacle. When an object is detected within 25 cm (10 in) of the sensors, the warning tone becomes continuous.The parking aid system is enabled when the ignition is in RUN and the transmission is in REVERSE. The system can be disabled through the message center RESET switch located in the instrument cluster. The parking aid menu is displayed until the transmission is taken out of REVERSE. While the menu is displayed, pressing the message center RESET switch will change the parking aid system status to OFF.The parking aid system will be disabled if a fault is detected in one of the 4 sensors, the parking aid speaker or the parking aid module. This will be indicated by the parking aid disabled warning CHECK PARK ASSIST displayed in the message center. The parking aid module is on the International Standards Organization (ISO) 9141 network and can be diagnosed with a diagnostic tool.
You can visual checks of the rear sensors for broken connectors or unplugged sensors. Other than that you will need to get it connected to a scanner that is able to communicate with the body sensors to pin point the problem. It could just be a sensor or wire it could be the module itself. Any other questions feel free to ask. Thank you, jim