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 engine control module (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 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

Component Connector End Views

Description and Operation

Object Detection Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for Scan Tool Information.

Ignition ON, transmission in reverse, block each of the object detect sensors on at a time. The appropriate display should illuminate indicating the object has been detected.

1. Ignition OFF, disconnect the harness connector at the rear object sensor control module.
2. Test for less than 1.0 ohm 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 ground.

⇒	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 ground.

⇒	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 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 matches the scan tool Vehicle Speed parameter in the ECM Engine Data List.

⇒	If the speedometer does not match 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 OFF, connect the harness connector at the rear object sensor control module.
7. Disconnect the harness connector at the rear parking assist display.
8. Ignition ON, verify a test lamp illuminates between the telltale assembly supply voltage circuit terminal A and ground.

⇒	If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the rear object sensor control module.

9. Connect a test lamp one at a time between the 12 volt supply circuit terminal A and the control circuits listed below:

•	Left amber LED control circuit terminal B

•	Center amber LED control circuit terminal C

•	Red LED control circuit terminal D

10. Ignition ON, transmission in reverse, place an object less than 0.3 m (11 in) away from the rear bumper. The test lamp should illuminate at each control circuit.

⇒	If the test lamp does not illuminate at any of the control circuits, test the appropriate control circuit for a short to voltage or an open/high resistance. If the circuits test normal, replace the rear object sensor control module.

11. If all circuits test normal, test or replace the rear parking assist display.

1. Ignition OFF, disconnect the harness connector at the RPA display.
2. Connect a 10A fused jumper wire between 12-volt reference circuit terminal A and B+.
3. Connect a 10A fused jumper wire between control circuit terminal and ground of the appropriate LED listed below:

•	Left amber LED control circuit terminal B

•	Center amber LED control circuit terminal C

•	Red LED control circuit terminal D

4. Verify that the appropriate LED illuminates.

⇒	If the component does not perform as specified, replace the RPA display.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.