Service Information

Cruze

DTC B138A

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: Control Module Voltage Reference Output 1 Circuit Low Voltage

DTC B138A 07: Control Module Voltage Reference Output 1 Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
8V Reference	B0958 06, B0959 06, B0960 06, B0961 06, B138A 03	B0958 06, B0959 06, B0960 06, B0961 06	B0958 06, B0959 06, B0960 06, B0961 06, B138A 07	--
Left Rear Object Sensor Signal	B0958 06	B0958 06	B0958 01	B0958 08, B0958 21
Left Middle Rear Object Sensor Signal	B0959 06	B0959 06	B0959 01	B0959 08, B0959 21
Right Middle Rear Object Sensor Signal	B0960 06	B0960 06	B0960 01	B0960 08, B0960 21
Right Rear Object Sensor Signal	B0961 06	B0961 06	B0961 01	B0961 08, B0961 21
Low Reference	--	B0958 06, B0959 06, B0960 06, B0961 06	--	--

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 8 V to the object sensors via the 8 V reference circuit and provides ground via the low reference circuit. The object alarm module triggers the sensors in a sequential loop. After each sensor transmits, the object alarm module uses the sensor ring received though 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.

Conditions for Setting the DTC

B138A 03

The object alarm module has detected the 8 V reference circuit is less than 7.2 V.

B138A 07

The object alarm 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 parking assist indicator in the instrument panel cluster will be activated.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

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

Ignition OFF, disconnect the harness connector at each of the object sensors.
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 Front and Rear 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 Front and Rear Parking Assist Control Module.

Connect each object sensor one at a time while monitoring the scan tool Park Assist Sensor Reference Voltage parameter. The parameter should be 7.2-9.2 V.

⇒	If not within the specified range, replace the appropriate object alarm sensor.

If all circuits test normal, replace the K41 Front and Rear Parking Assist Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Rear Parking Assist Alarm Sensor Replacement

•	Control Module References for Object Alarm Module replacement, setup and programming