GM Service Manual Online
For 1990-2009 cars only

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

DTC Descriptors

DTC B0958 01: Park Assist Sensor Rear Left Outer Circuit Malfunction

DTC B0958 06: Park Assist Sensor Rear Left Outer Circuit Open or Low Voltage

DTC B0958 08: Park Assist Sensor Rear Left Outer Invalid Signal

DTC B0958 21: Park Assist Sensor Rear Left Outer Circuit Incorrect Period

DTC B0959 01: Park Assist Sensor Rear Left Middle Circuit Malfunction

DTC B0959 06: Park Assist Sensor Rear Left Middle Circuit Open or Low Voltage

DTC B0959 08: Park Assist Sensor Rear Left Outer Invalid Signal

DTC B0959 21: Park Assist Sensor Rear Left Outer Circuit Incorrect Period

DTC B0960 01: Park Assist Sensor Rear Right Middle Circuit Malfunction

DTC B0960 06: Park Assist Sensor Rear Right Middle Circuit Open or Low Voltage

DTC B0960 08: Park Assist Sensor Rear Right Middle Invalid Signal

DTC B0960 21: Park Assist Sensor Rear Right Middle Circuit Incorrect Period

DTC B0961 01: Park Assist Sensor Rear Right Outer Circuit Malfunction

DTC B0961 06: Park Assist Sensor Rear Right Outer Circuit Open or Low Voltage

DTC B0961 08: Park Assist Sensor Rear Right Middle Invalid Signal

DTC B0961 21: Park Assist Sensor Rear Right Middle Circuit Incorrect Period

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

8-Volt Reference

B0958 06, B0959 06, B0960 06, B0961 06, B138A 03

B0958 06, B0959 06, B0960 06, B0961 06, B138A 03

B138A 07

--

Left Rear Corner Object Sensor Signal

B0958 06

B0958 06

B0958 01

B0958 08, B0958 21

Left Rear Middle Object Sensor Signal

B0959 06

B0959 06

B0959 01

B0959 08, B0959 21

Right Rear Middle Object Sensor Signal

B0960 06

B0960 06

B0960 01

B0960 08, B0960 21

Right Rear Corner Object Sensor Signal

B0961 06

B0961 06

B0961 01

B0961 08, B0961 21

Low Reference

--

B0958 06, B0959 06, B0960 06, B0961 06

--

--

Circuit/System Description

The object sensors are 3-wire sensors that are used to determine the distance between the vehicle and an object of interest. The object alarm module supplies an 8 V reference and ground reference to each of the object sensors. The object alarm module triggers the sensors in a sequential loop. After each sensor transmits, the object alarm module uses the sensor ring received through the signal circuit to calculate the distance and position of an object.

Conditions for Running the DTC

    • DTC B1325 is not set
    • The ignition voltage is at least 9.0 V and no more than 16.0 V
    • Transmission is in DRIVE or REVERSE

Conditions for Setting the DTC

B0958 01, B0959 01, B0960 01 or B0961 01

The rear object sensor signal circuit detects a voltage greater than 11.5 V.

B0958 06, B0959 06, B0960 06 or B0961 06

The rear object sensor signal circuit detects a voltage less than 0.5 V.

B0958 08, B0959 08, B0960 08 or B0961 08

The object alarm module detects an invalid signal.

B0958 21, B0959 21, B0960 21 or B0961 21

The rear object sensor determines no change in the position of an object while the vehicle is in motion.

Action Taken When the DTC Sets

    • Parking assist is disabled.
    • SERVICE PARK ASSIST message is displayed in the driver information center and a chime will sound.

Conditions for Clearing the DTC

    • The object alarm module clears the history DTC when a current DTC is not detected in 100 ignition cycles.
    • The condition for the DTC is no longer present.

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Verify that DTC B138A is not set.
  2. If DTC is set, refer to DTC B138A.
  3. Park brake OFF, transmission in REVERSE, individually place a suitable object behind each sensor. Verify the appropriate scan tool Rear Region parameter is between Zone 1 and Zone 4.

Circuit/System Testing

Single Object Sensor DTC Set

  1. Ignition OFF, disconnect the harness connector at the appropriate object sensor.
  2. Ignition OFF for 30 seconds, test for less than 5 Ω between the low reference circuit terminal 2 and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the object alarm module.
  4. Ignition ON, transmission in REVERSE, test for 7.2 - 9.2 V between the voltage reference circuit terminal 1 and ground.
  5. If greater than the specified range, test the voltage reference circuit for a short to voltage. If the circuit tests normal, replace the object alarm module.
    If less than the specified range, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the object alarm module.
  6. Ignition OFF, remove the malfunctioning object sensor and swap locations with another properly functioning rear object sensor. Connect the harness connector at both sensors.
  7. Ignition ON, verify the DTC is set for the new location in which the malfunctioning sensor is installed.
  8. If the DTC does not set for the new location, test the signal circuit terminal 3 for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the object alarm module.
  9. If the DTC sets for the new location in which the malfunctioning sensor is installed, replace the appropriate rear object sensor.

Multiple Object Sensor DTCs Set

  1. Ignition OFF, disconnect the harness connector at each of the object sensors.
  2. Ignition OFF for 30 seconds, test for less than 5 Ω between the low reference circuit terminal 2 and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the object alarm module.
  4. Ignition ON, transmission in REVERSE, test for 8.0 - 9.0 V between the voltage reference circuit terminal 1 and ground.
  5. If greater than the specified range, test the voltage reference circuit for a short to voltage. If the circuit tests normal, replace the object alarm module.
    If less than the specified range, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the object alarm module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Rear Object Sensor Replacement
    •  Control Module References for object alarm module replacement, setup, and programming