Rear Parking Assist Malfunction
Rear Parking Assist Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.
Circuit/System Description
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 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.
Diagnostic Aids
* The RPA system is equipped with an on-board diagnostic display feature capable of displaying diagnostic trouble codes from the RPA display. Before using this diagnostics, it is necessary to get familiar and understand how the on-board diagnostic feature operates. Refer to Diagnostic Trouble Code (DTC) Displaying (Diagnostic Trouble Code (DTC) Displaying) and to Diagnostic Trouble Code (DTC) Clearing (Diagnostic Trouble Code (DTC) Clearing) on how the diagnostic trouble codes are displayed and cleared from the RPA display system.
* Make sure the rear park assist (RPA) object sensors located on the vehicle rear bumper are clean and clear. Remove any objects that is blocking the sensors.
* Inspect for after market devices which could affect the operation of the RPA system.
Reference Information
Schematic Reference
Object Detection Schematics ([1][2]Collision Avoidance and Parking Assist Systems)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Object Detection Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning)for Scan Tool Information.
Circuit/System Verification
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.
Circuit/System Testing
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 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 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 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. Ignition OFF, disconnect the harness connector at the Rear Object Sensor Control Module.
10. Connect the harness connector at the Rear Parking Assist Display.
11. Connect a 3A fused jumper wire between the telltale assembly supply voltage circuit terminal 23 and B+.
12. Ignition ON, connect a jumper wire between the following telltale assembly indicator control circuits and ground. When the telltale circuit is jumpered to ground, the indicator should illuminate.
* Telltale assembly indicator control circuit terminal 24
* Telltale assembly indicator control circuit terminal 25
* Telltale assembly indicator control circuit terminal 26
• If any of the indicators do not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the RPA display.
13. If all circuits tests normal, replace the rear object sensor control module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Information Center Telltale Assembly Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for the object sensor control module, ECM or BCM replacement, setup, and programming