Parking Assist Distance Sensor: Description and Operation

Park Assist Sensor

Description






Vehicles equipped with the park assist system have four park assist sensors (1) installed on the rear bumper fascia. Only the membrane (3) of each sensor is visible through a hole in the outer vertical surface of the fascia. The remainder of each sensor including the sensor mounting bracket, the sensor spacer and the sensor wiring connection is concealed behind the fascia. A sensor wire harness behind the fascia connects the sensors to the vehicle electrical system.

Each of the four sensors is identical in construction and is interchangeable. The electronic circuitry and a communication chip for each sensor is enclosed and protected within the molded black plastic sensor housing. The housing includes an integral connector receptacle (4) and two integral latch tabs (2). The sensor membrane extends from the surface of the sensor housing, and is finished to match or contrast with the outer surface of the fascia.






The numbering system for the park assist sensors allows for up to twelve sensors on the vehicle, six front and six rear. The sensors are numbered in a clockwise manner starting at the left front bumper. The left front sensor (if equipped with front park assist) is the number 1 sensor. The numbering continues in a clockwise direction around the vehicle. Since this vehicle uses only four rear sensors, sensor numbers 7 and 12 are omitted, so the left rear sensor is the number 11 sensor.

A resilient O-ring spacer around the circumference of each of the four sensor membranes isolates the membrane from the openings in the fascia. Each sensor is snapped into its own dedicated molded plastic mounting bracket. Each mounting bracket is heat-staked to the back side of the rear fascia.

The park assist sensors cannot be adjusted or repaired. If ineffective or damaged they must be replaced. The sensors and the spacers are each available for individual service replacement.

Operation

The park assist sensors are ultrasonic transceivers that are completely controlled by the park assist module. The sensors transmit and receive ultrasonic signals. The sensors each receive battery current and ground in parallel from the module, but are each connected to individual dedicated serial bus communication circuits to the module.

Each sensor membrane is oscillated, then quieted by the module in a pulsing fashion. While the sensor membrane oscillates, it emits an ultrasonic signal. This signal will bounce or echo off of objects in the path of the vehicle. While quieted, each membrane receives the echoes of the ultrasonic signals it and the other sensors have transmitted. The sensors then communicate this echo data over the serial bus lines back to the module. The microprocessor in the module uses the intervals between the ultrasonic transmission and reception data from the sensors to calculate the distance to any obstacles identified by the ultrasonic echoes.

The hard wired circuits between components related to the park assist sensors may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the park assist sensors or the electronic controls or communication between modules and other devices that provide some features of the park assist system. The most reliable, efficient, and accurate means to diagnose the park assist sensors or the electronic controls and communication related to park assist sensor operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.