B138A

DTC B138A

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC B138A 03
- Control Module Voltage Reference Output Circuit Low Voltage

DTC B138A 07
- Control Module Voltage Reference Output Circuit High Voltage

Diagnostic Fault Information





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 parking assist control module supplies 8 V to the object sensors via the 8 V reference circuit and provides ground via the low reference circuit. The parking assist control module triggers the sensors in a sequential loop. After each sensor transmits, the parking assist control module uses the sensor echo received through the signal circuit to calculate the distance and position of an object.

Conditions for Running the DTC

* Ignition ON
* The parking assist is activated. The activation takes place through putting in the reverse gear or through operating the parking assist switch.

Conditions for Setting the DTC

B138A 03

The parking assist control module has detected the 8 V reference circuit is less than 7.2 V.

B138A 07

The parking assist control module has detected the 8 V reference circuit is greater than 9.2 V.

Action Taken When the DTC Sets

* The parking assist is disabled.
* The driver information center displays SERVICE PARK ASSIST.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information
Schematic Reference

Object Detection Schematics ([1][2]Collision Avoidance and Parking Assist Systems)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Object Detection Description and Operation (UVC) (Object Detection (UVC))Object Detection Description and Operation (UD5) (Object Detection Description and Operation (UD5))
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)

Circuit/System Verification

Ignition ON, activate the parking assist, observe the scan tool Park Assist Sensor Reference Voltage parameter. The reading should be 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, activate the park assist, test for 7.5-9.0 V between the 8 V reference circuit terminal 1 at the B78G Rear Object Sensor - Left Outer harness connector and ground.

• If less than the specified range, test the 8 V reference circuit for a short to ground. If the circuit tests normal, replace the K41 Parking Assist Control Module.
• If greater than the specified range, test the 8 V reference circuit for a short to voltage. If the circuit tests normal, replace the K41 Parking Assist Control Module.

3. Install each object alarm 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 alarm sensor that was connected immediately before the DTC set.

4. If all circuits test normal, replace the K41 Parking Assist Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests).

* Front Object Alarm Sensor Replacement (Front Object Alarm Sensor Replacement)
* Rear Object Sensor Replacement (Rear Object Sensor Replacement)
* Control Module References (Programming and Relearning)