Object Detection Description and Operation (RPA)

WARNING: This page is about a different car, the 2008 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

The object alarm system monitors the distance and how close a vehicle is to an object when backing up in a parking maneuver. The object alarm system will notify the driver of any objects of interest when backing up at speeds less than 5 km/h (3 mph). The distance between a vehicle and an object of interest is monitored by the 4 ultrasonic sensors located in the rear bumpers of the vehicle. The object sensors receive the echo signals reflected off an object of interest while the vehicle is backing up at speeds less than 5 km/h (3 mph). The rear object sensor control module receives the vehicle speed input from the ECM via the vehicle speed signal circuit. When the backing up speed exceeds 5 km/h (3 mph), the rear parking assist (RPA) system is disabled. The object detection system uses visual displays and audible warnings from the radio speakers to warn the driver of an object of interest within the defined field of view. The rear integration module (RIM) controls the RPA chime function via the chime control circuit and will send serial data request to the radio to sound the chime as needed. The visual RPA display comprises of two amber and one red indicators and these indicators illuminate based on the vehicle distance to the object of interest. When the RPA system is activated the RPA display first performs a bulb check before any normal operation. The object sensor is a three wire sensor comprising of the supply voltage circuit, signal circuit and the low reference circuit. Power and ground is provided to the object sensors from the rear object sensor control module via the object sensor supply voltage circuit and low reference circuit. The typical object sensor signal circuit voltage when the system is active is between 7.2-9.2V. The object detection system is initiated when the rear object sensor control module receives the transmission reverse input from the RIM via the backup lamp supply voltage circuit.

When the ignition is ON and the vehicle is placed into reverse, the RPA performs a bulb check. During the bulb check, the 3 indicators on the display illuminate for approximately 2 seconds to indicate that the system is working. The RPA performs a bulb check and operates when the following conditions are present:

The ignition is ON.
The vehicle is placed in REVERSE (R).
The vehicle speed is less than 5 km/h (3 mph).
At speeds greater than 5 km/h (3 mph), the RPA is disable. The red indicator flashes to warn the driver that the RPA is disabled.

The RPA senses how close the vehicle is to an object. The distance is determined by the 4 ultrasonic sensors located on the rear bumper. When the system detects an object, one of the following will occur:

If the object is less than 0.3 m (11 in) away from the rear of the vehicle, the amber outside, amber middle, and the red outside indicators flash and the chime sounds continuously.
If the object is less than 0.3-0.5 m (11-20 in) away from the rear of the vehicle, the amber outside, amber middle, and the red outside indicators are on and the chime sounds continuously.
If the object is 0.5-1.0 m (20-40 in) away from the rear of the vehicle, the amber outside, and the amber middle indicators are on.
If the object is 1.0-1.5 m (40-60 in) away from the rear of the vehicle, the amber outside indicator is on and the chime sounds one time on the first detection of an object.

The RPA can detect objects 7.6 cm (3 in) wide and at least 25.4 cm (10 in) tall. It cannot detect objects above the level of the roof.

If the red indicator flashes continuously, the on-board diagnostic needs to be entered to determine if a malfunction is present. Refer to Diagnostic Trouble Code (DTC) Displaying .