For 1990-2009 cars

### 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 B138A 03: Device Voltage Reference Group 1 Outputs Voltage Below Threshold
DTC B138A 07: Device Voltage Reference Group 1 Outputs Voltage Above Threshold

### 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 | B0960 08, B0960 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 vehicle is in REVERSE

### Conditions for Setting the DTC

#### B138A 03

The object alarm module detects the sensor 8 V reference circuit is less than 7.2 V.

#### B138A 07

The object alarm module detects the sensor 8 V reference circuit is greater than 9.2 V.

### Action Taken When the DTC Sets

• | Parking assist system is disabled.

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

### Conditions for Clearing

• | 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

Ignition ON, transmission in REVERSE, verify that the scan tool Sensor Supply Voltage parameter is between 7.2 - 9.2 V.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at each of the object sensors.
2. Ignition ON, verify DTC B138A is not set as current.

⇒ | If the DTC is set, test the 8 V reference circuit terminal 1 for a short to voltage, short to ground, or an open/high resistance. If circuit tests normal, replace the object alarm module.

3. Install each sensor harness connector one at a time, checking DTCs after each sensor is connected. Verify DTC B138A is not set as current.

⇒ | If the DTC is set, replace the object sensor that was connected immediately before the DTC set.

### 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.