GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Sierra Denali 🢒 Safety and Security 🢒 Object Detection 🢒 Parking Assist 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.

Circuit/System Description

The parking assist system is designed to identify and notify the driver of an object in the vehicle's path when reversing at speeds of less than 8 km/h (5 mph). The distance and location of the object is determined by four object sensors located in the rear bumper. The parking assist system will notify the driver using the parking assist indicators and an audible signal through the radio.

Diagnostic Aids

The scan tool Park Assist Disable History parameters are a list of the seven previous reasons the park assist system was disabled. These parameters may help in the diagnosis of an intermittent concern or a customer concern which is the result of normal system operation. The following is a brief description of potential causes which may aid in diagnosis:

    • Manual Disable - The park assist system has been disabled by the vehicle operator through the DIC.
    • Park Brake - The vehicle parking brake is applied or a malfunction exists within the parking brake system.
    • Hitch/Object Attached - The object alarm module is detecting an object that is attached to the vehicle. Common items such as a hitch receiver, trailer, or a bicycle rack may cause this concern. Additionally, damage to the rear of the vehicle or a misaligned sensor may cause this concern. If the vehicle is damaged in a manner that causes the sensor to detect the bumper itself, the object alarm module will interpret this as an attached object and disable the system. Carefully inspect the bumper, bumper mounting surface, and sensor retainers before continuing with normal diagnosis.
    • Reverse Overspeed - The vehicle is traveling too fast in reverse at speeds of greater than 8 km/h (5 mph).
    • Sensor Disturbance - An outside interference is causing sensor movement. Such interference may be caused a heavy pounding, like that of a nearby jackhammer, or large changes in pressure, such as a large truck's air brakes.
    • Snow/Ice/Mud - One or more of the sensors is being blocked by snow, mud, ice, or other debris.
    • Sensor Ring Time - Each of the sensors emits an ultrasonic frequency. This frequency is reflected off of nearby objects, bouncing it back towards the vehicle bumper where it is received by the sensor. The time between the sensor emitting the frequency and the sensor receiving the reflection, known as sensor ring time, is used to determine the distance of nearby objects. Excessive paint thickness on a sensor may cause an excessive sensor ring time. When replacing or refinishing a sensor, do not apply an excessive amount of paint or clear coat.

Reference Information

Schematic Reference

Object Detection Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Object Detection 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, verify the park assist system is enabled through the DIC.
    2. ⇒If the park assist system is manually disabled, enable the system. Refer to the vehicle owners manual for instructions on enabling the system.
  2. Observe the scan tool Park Assist Switch parameter while pressing and releasing the park assist disable switch. The parameter should change between Active and Inactive.
    3. ⇒If the parameter does not cycle between the specified values, refer to Park Assist Disable Switch Circuit Malfunction.
  3. Observe the scan tool Park Assist Switch LED parameter while pressing and releasing the park assist disable switch. The parameter should change between On and Off.
    4. ⇒If the parameter does not cycle between the specified values, refer to Park Assist Disable LED Circuit Malfunction.
  4. Command each of the park assist indicator LEDs ON and OFF with a scan tool. Each of the LEDs should turn ON and OFF as commanded.
    5. ⇒If any of the LEDs do not turn ON and OFF, refer to Parking Assist Indicator Malfunction.
  5. Ignition ON, vehicle in reverse, verify the scan tool Park Assist System Status parameter is Enable.
    6. ⇒If not the specified value, refer to Diagnostic Aids and the scan tool Park Assist Disable History parameters to determine the cause of the inhibit.

Circuit/System Testing

Park Assist Disable Switch Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector I/P multifunction switch assembly.
  2. Test for less than 10 ohms between the ground circuit terminal 3 and ground:
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Park Assist Switch parameter is Inactive.
    4. ⇒If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the object alarm module.
  4. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Park Assist Switch parameter is Active.
    5. ⇒If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the object alarm module.
  5. If all circuits test normal, test or replace the I/P multifunction switch assembly.

Park Assist Disable LED Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector I/P multifunction switch assembly.
  2. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 6 and ground:
    3. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, connect the harness connector at the I/P multifunction switch assembly. Disconnect the X1 harness connector at the object alarm module.
  4. Ignition ON, verify the park assist disable LED is not illuminate.
    5. ⇒If the LED is illuminated, test the control circuit for a short to ground. If the circuit tests normal, test or replace the I/P multifunction switch assembly.
  5. Install a 10A fused jumper wire between the control circuit terminal 3 and ground. Verify the park assist disable LED is illuminated.
    6. ⇒If the LED is not illuminated, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the I/P multifunction switch assembly.
  6. If all circuits test normal, replace the object alarm module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Accessory Switch Replacement
    •  Control Module References for object alarm module replacement, setup, and programming