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 aid (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 body control module (BCM) controls the RPA chime function via the chime control circuit and sends serial data request to the radio to activate 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 V-9.2 V. The object detection system is initiated when the rear object sensor control module receives the transmission reverse input from the BCM via the backup lamp supply voltage circuit.

Schematic Reference

Object Detection Schematics

Connector End View Reference

Object Detection Connector End Views

Description and Operation

Object Detection Description and Operation

Electrical Information Reference

1. Ignition OFF, disconnect the harness connector at the rear object sensor control module.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminal 12 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates when connected between the ignition 1 voltage circuit terminal 13 and the ground circuit terminal 12.

⇒	If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance.

4. Ignition ON, transmission in reverse, verify that a test lamp illuminates when connected between the backup lamp supply voltage circuit terminal 15 and the ground circuit terminal 12.

⇒	If the test lamp does not illuminate, test the backup lamp supply voltage circuit for a short to ground or an open/high resistance. If circuit tests normal replace the body control module (BCM).

5. Start the engine, scan tool installed, with the vehicle drive wheels raised and the vehicle placed in drive or 1st gear. Verify that the speedometer value does not match the scan tool Vehicle Speed parameter in the ECM Engine Data List.

⇒	If the speedometer matches the scan tool Vehicle Speed parameter, test the vehicle speed signal circuit terminal 18 for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. Ignition ON, with the telltale assembly supply voltage circuit terminal 23 connected to B+ and the display indicator control circuit terminal(s) 24, 25 and 26 connected to the ground circuit terminal 12 one at a time. Verify that each rear parking assist display indicator illuminates when each indicator control circuit is connected to ground.

⇒	If one or two RPA indicators does not illuminate, test the indicator control circuit(s) for a short to voltage or an open/high resistance. If the circuit(s) tests normal, replace the RPA display.

⇒	If all the RPA display indicators do not illuminate, test the telltale assembly supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the RPA display.

7. If all circuit(s) tests normal, replace the rear object sensor control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.