Buick Regal: Rear Cross Traffic Alert System Malfunction

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

1. Rear Cross Traffic Alert Malfunction

Circuit/System Description

The side object sensor modules are located on each side of the vehicle behind the rear fascia and are not directly visible from outside the vehicle. The same sensors are also used for side blind zone alert. The sensors use radar to determine the presence of objects near the back of the vehicle. When an object is detected in the rear cross traffic zone, the module will send out a signal through serial data communication to turn on the visual icons and also audio chime or haptic notification. Each sensor is supplied B+ and ground. The right sensor receives an additional ground. Both sensors communicate independently on the serial data line. The serial data enters the left sensor in a pass-thru configuration, that connects to the right sensor. The scan tool is able to individually communicate with each sensor.

Diagnostic Aids

• The rear cross traffic alert system uses the same sensors as side blind zone alert so a malfunction may affect either or both systems.
• The conditions for disabling the rear cross traffic alert system are captured by DTCs. The drivers information center will display Service Side Detection System if one of the sensors has failed. A B101E 47 Electronic Control Unit Software VIN Not Programmed DTC in history will not affect sensor operation and the module should not be replaced for this DTC.
• The rear cross traffic system can be disabled if any off the following occur:
  • The driver has selected the Off mode through vehicle personalization menus. The selected mode is retained over ignition cycles. A driver information center message stating that the Rear Cross Traffic System Alert Off shall be displayed.
  • There is a loss of serial data communication with a sensor or between modules.
• The side blind zone may be temporarily unavailable due to the following:
  • A blockage condition exists (i.e. mud/snow buildup in front of the sensor). A driver information message "Side Detection System Unavailable" will be displayed. The side blind zone system transitions back to the normal operating state when the blockage is removed.

    Bumper sticks, fascia damage, labels, and heavy rain storms may also cause this condition.

    The blockage determination is performed with the vehicle in a drive gear.

  • The rear cross traffic alert system will read the GPS latitude and longitude on the serial data bus and calculate if the vehicle is within a Radio Astronomy zone. These zones are located in Europe and Japan and require the sensors to be turned off. The "Side Detection System Unavailable" message will be displayed to the driver when this occurs.
• Because the sensors are identical, they may be swapped from one side of the vehicle to the other in an attempt to isolate a concern. Sensors should NOT be swapped from one vehicle to another.
• The rear cross traffic alert system is designed to ignore stationary objects; however, the system may occasionally detect pedestrians, shopping carts, or other objects. This is normal system operation and does not require service.
• The rear cross traffic alert system may indicate an object if a trailer is attached to the vehicle, or a bicycle or object is extending out to either side of the vehicle. This is normal operation and does not require service.

Reference Information

Schematic Reference

Driver Assistance Systems Wiring Schematics

Connector End View Reference

Master Electrical Component List

Description and Operation

Cross Traffic Alert Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON.

2. Verify that no DTCs are set.

• If any DTC is set

Refer to: Diagnostic Trouble Code (DTC) List - Vehicle

• Go to next step: If no DTC is set

3. Verify the scan tool can communicate with the left side object sensor.

• If the scan tool can not communicate with the left side object sensor

Refer to Circuit/System Testing - Left Side Object Sensor Malfunction.

• Go to next step: If the scan tool can communicate with the left side object sensor

4. Verify the scan tool can communicate with the right side object sensor.

• If the scan tool can not communicate with the right side object sensor

Refer to Circuit/System Testing - Right Side Object Sensor Malfunction.

• Go to next step: If the scan tool can communicate with the right side object sensor

5. Verify that the rear cross traffic indicators turn ON and then turn OFF when commanding the Rear Cross Traffic Visual Alert Indicators ON and OFF with a scan tool.

• If alert indicators do not turn ON and OFF

1. Verify the system is enabled.
   • If disabled, refer to diagnostic aids for cause of disable.
   • If enabled test or replace the display.

• Go to next step: If indicators turn ON and OFF

6. Verify that the audible alert turns ON and then turn OFF when commanding the Rear Cross Traffic Audible Alert ON and OFF with a scan tool.

• If the audible alert does not turn ON and OFF

1. Verify the system is enabled.
   • If disabled, refer to diagnostic aids for cause of disable.
   • If enabled refer to audio system malfunction.

• Go to next step: If audible alert turns ON and OFF

7. All OK.

Circuit/System Testing

Left Side Object Sensor Malfunction

1. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connector at the B218L Side Object Sensor Module - Left.

2. Test for less than 10 Ω between ground circuit terminal 7 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Verify a test lamp illuminates between the B+ circuit terminal 8 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition Off.
2. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the B218L Side Object Sensor Module - Left.

• Go to next step: If the test lamp illuminates

4. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.

5. Test for less than 2 Ω in each of the serial data circuits end to end between the control module harness connector terminal 2 and the DLC terminal 1.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

6. Replace B218L Side Object Sensor Module - Left.

Right Side Object Sensor Malfunction

1. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connector at the B218R Side Object Sensor Module - Right.

2. Test for less than 10 Ω between the following ground circuit terminals and ground.

• Terminal 3
• Terminal 8
• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Verify a test lamp illuminates between the B+ circuit terminal 5 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.
2. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the B218R Side Object Sensor Module - Right.

• Go to next step: If the test lamp illuminates

4. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.

5. Test for less than 2 Ω in each of the serial data circuits end to end between the control module harness connector terminal 7 and the DLC terminal 1.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

6. Replace B218R Side Object Sensor Module - Right.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for control module replacement, programming and setup.

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