_GM (UD7) - Parking Assist

Description and Operation

The parking assist system is designed to identify and notify the driver of an object in the vehicle 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 fascia. The parking assist system will notify the driver using audible beeps through the radio. The parking assist system is made up of the following components:

• Rear parking assist control module
• Rear object sensors
• Radio

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Parking Assist Control Module

The rear parking assist control module provides a reference voltage and a low reference to the four object alarm sensors. The rear parking assist control module receives individual signals from each of the four sensors and determines the location and distance of an object based on these inputs. When an object is detected, the rear parking assist control module will send a data message via serial data to the radio requesting an audible alert.

Object Sensors

The object sensors are located in the rear fascia. The sensors are used to determine the distance between an object and the rear of the vehicle. Each sensor emits an ultrasonic frequency which is reflected off an object behind the vehicle. These reflections are received by the sensors. The time difference between the emission of the frequency and when the reflection is received is known as sensor echo time, it is used to determine the distance to the object. The sensors report this, information to the rear parking assist control module.

Radio

The radio controls the audible alert for the park assist alert. If the an object is detected the radio will command beeps as an audible alert to the driver.

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Parking Assist Operation

When an object is within the measuring range of the sensor, the ultrasonic pulse is reflected and is received by the sending or a neighboring sensor. The sensor converts this signal into a voltage signal and sends this signal to the rear parking assist control module. The rear parking assist control module evaluates the received sensor signals. As soon as an object is within the measuring range, the rear parking assist control module sends a message via serial data to the radio to provide an alert signal.

The parking assist system can detect objects greater than 7.6 cm (3 in) wide and 25.4 cm (10 in) tall. The system cannot detect objects below the bumper, underneath the vehicle.

The parking assist can be activated and deactivated by pressing the parking assist switch. When REVERSE gear is selected, park assist is automatically activated. By subsequently pressing the parking assist switch the parking assist can be disabled again. The rear parking assist control module carries out a self test and monitors the sensors for electrical and mechanical faults. Monitored is the power supply of each sensor and the sensor signals, which need to alter when the vehicle moves. If this is not the case, the sensor is acoustically blocked or faulty. Mud, ice and snow may cause obstruction of the function of the sensors. The rear parking assist control module also checks whether the correct type of sensor is installed. If any of these tests fails, a DTC with corresponding symptom is set, the parking assist is deactivated and the parking assist indicator in the instrument panel cluster is activated.

Parking Assist System Driver Information Center Messages

    SERVICE PARK ASSIST    

The driver information center displays SERVICE PARK ASSIST when the rear parking assist control module detects a malfunction in the parking assist system and the system is disabled. The driver information center also displays SERVICE PARK ASSIST when a loss of communication occurs with the rear parking assist control module.

    PARK ASSIST OFF    

The PARK ASSIST OFF message is displayed in the driver information center when the parking assist system is disabled due to conditions that disable or inhibit the system. The rear parking assist control module requests the driver information center display PARK ASSIST OFF when it detects that one of the following conditions:

• • • The parking assist system is manually disabled using the parking assist switch.
    • An object is attached to the rear of the vehicle, such as a trailer, bicycle rack, trailer hitch receiver, or tow bar. Also, an object extending beyond a lowered tailgate will disable the system.
    • The parking assist sensors are covered by snow, mud, dirt, slush, or ice.
    • The rear fascia is damaged.
    • Excessive paint thickness on a replacement parking assist sensor.
    • The parking assist sensors are disrupted by vibrations, like those caused by a large nearby vehicle or from heavy equipment such as a jackhammer.

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Schematics