GM Service Manual Online
For 1990-2009 cars only

Ultrasonic rear parking assist (URPA) can help a driver determine how close an object is to the rear bumper within a given area, making parking easier.

The information center telltale assembly is located inside the vehicle, above the rear window. It has three color-coded lights that can be seen through the rearview mirror or by turning around.

URPA comes on automatically when the shift lever is moved into REVERSE (R) and the vehicle speed is less than 5 km/h (3 mph). When the system comes on, the three lights on the display illuminate to let you know that the system is working. URPA senses how close your vehicle is to an object. The distance is determined by the four ultrasonic sensors located on the rear bumper. When shifting into REVERSE (R) and an object is detected, one of the following will occur:

    • Less than 12 in (0.3 m) -- Amber/Amber/Red lights flashing and continuous chime.
    • 12 to 20 in (0.3 to 0.5 m) -- Amber/Amber/Red lights on and continuous chime
    • 20 to 40 in (0.5 to 1.0 m) -- Amber/Amber Lights On
    • 40 in to 5 ft (1.0 to 1.5 M) -- Amber Light

URPA can detect objects 3 in (7.6 cm) and wider, and at least 10 inches (25.4 cm) tall, but it can not detect objects above the level of the rear compartment. In order for the rear sensors to recognize an object, it must be within operating range.

If the URPA system is not functioning properly, the display flashes red, indicating that there is a problem.

Rear Object Sensor Control Module Connector

The rear object sensor control module connector (harness side) has a retainer (1) and cover (2) as well as a secondary lock (5). The secondary lock must be removed from the connector body (3) before removing or installing connector terminals.


Object Number: 598147  Size: LH
(1)Retainer
(2)Cover
(3)Connector Body
(4)Pin Header (Part of the Module)
(5)Secondary Lock

URPA Self-Diagnostic Information

During normal operation of the vehicle, the rear object sensor control module has the ability to detect many failures within the system, such as an open circuit or a short to ground on one of the rear object sensor circuits. If the module detects one of the failures it is programmed to recognize, the module causes the information center telltale assembly to flash the red indicator. The module disables operation of the URPA system under this condition (Red Indicator Flashes).

In the Red Indicator Flashes operation of the URPA system, the module internally stores one or more diagnostic codes. Each stored code may be displayed as a pattern of the three indicators on the information center telltale assembly. To display the patterns, the URPA module must be in diagnostic mode. A technician initiates the diagnostic mode by grounding the rear parking assist diagnostic connector. The specific steps to clear the diagnostic codes and to enter the diagnostic mode are provided below.

Clearing Self-Diagnostic Information

URPA diagnostic codes may be cleared in one of two ways. (The rear parking assist diagnostic connector must be not grounded in order to clear the stored codes.)

Clearing Self-Diagnostic Information (Driving the Vehicle)

  1. Drive the vehicle forward at least 24 km/hr (15 mph).
  2. Stop the vehicle.
  3. Turn OFF the ignition.

Clearing Self-Diagnostic Information (Vehicle Stopped)

  1. Turn ON the ignition, then shift into REVERSE within five seconds.
  2. Turn OFF the ignition.

Displaying Self-Diagnostic Information

The steps to read the URPA diagnostic codes are as follows.

  1. Turn OFF the ignition.
  2. Locate the diagnostic connector and remove the connector cover.
  3. Connect a fused jumper from the diagnostic connector to ground.
  4. Clear the field of vision. Specifically, this action means the following:
  5.  - Remove all objects resting on the rear compartment lid.
     - Remove objects less than 2 meters (6.5 ft) from the rear bumper.
     - Remove objects less than 0.5 meters (1.6 ft) from the side of the vehicle.
  6. Turn ON the ignition.
  7. Move the gear shifter to REVERSE within five seconds.
  8. Observe the telltale assembly. The following telltale pattern should appear. (This pattern indicates that the module has entered the diagnostic mode.)
  9. • Yellow Outside Indicator - On
    • Yellow Center Indicator - Off
    • Red Indicator - On

The diagnostic codes, or patterns, appear automatically on the telltale assembly. If the module has more than one stored code, the patterns for each code flash one after the other. The specific patterns are explained within the procedure Rear Parking Assist Inoperative -- Red Indicator Flashes.