SAAB WIS ONLINE

Liftgate Object Sensor Malfunction - DTC B153F

Liftgate Object Sensor Malfunction - DTC B153F

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 B153F 02

Liftgate Object Sensor Signal Circuit Short to Ground

DTC B153F 05

Liftgate Object Sensor Signal Circuit Short to Battery or Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Signal B153F 02 B153F 05 B153F 05 -
Left/Right Object Sensor Signal B153F 02 B153F 05 B153F 05 -
Low Reference - B153F 05 B153F 05 -


Circuit/System Description

The liftgate object sensors are pressure sensitive touch tapes located on either side of the upper inside edge of the liftgate panel. The two tape switches are placed in series between the liftgate object sensor signal circuit and the liftgate object low reference circuit. Each object sensor has a resistor as well as a switch. The resistors enable the liftgate control module to perform diagnostic functions on the circuits. When both touch tape sensors are not pressed, the 5 volt reference voltage supplied by the liftgate control module passes through the resistors and the liftgate control module detects approximately 3.3 volts. Pressing a touch tape will cause the voltage to drop to approximately to 2.5 volts indicating an obstruction is present. If the liftgate is in the open position, the liftgate control module will prohibit liftgate movement. If the obstruction occures during the power close function, the liftgate control module will command the liftgate to reverse direction.

Conditions for Running the DTC

The system voltage is 9-16 V.

Conditions for Setting the DTC

B153F 02

The liftgate control module detects a short to ground in the liftgate tape switch signal circuit for greater than 10 minutes.

B153F 05

The liftgate control module detects a short to voltage or an open/high resistance in the liftgate tape switch signal circuit or an open/high resistance in the low reference circuit for greater than 10 minutes.

Action Taken When the DTC Sets

The liftgate control module will prevent any movement of the liftgate while attempting to command the liftgate to power close.

Conditions for Clearing the DTC


The DTC will be current for as long as the fault is present.

When the fault is no longer present, the DTC will be a history DTC.

A history DTC will clear after 50 ignition cycles.


Diagnostic Aids


If the liftgate will not release from the closed position, refer to Opening the Liftgate Without Electrical Power for the appropriate procedure

Whenever the liftgate control module loses power or is disconnected, the ignition must be cycled OFF then ON in order to reactivate the liftgate control module.

If the liftgate mode switch is in the Off position, the liftgate will only open and close manually. Before testing the liftgate for power open and power close functions, verify that the liftgate mode switch is in the ¾ or MAX position.


Reference Information

Schematic Reference

Liftgate Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Liftgate Description and Operation

Electrical Information Reference


Testing for Intermittent Conditions and Poor Connections

Circuit Testing

Wiring Repairs

Connector Repairs


Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification


1. DTC B153F should not be set as history.

2. If DTC B153F is set only as history, replace both B71 liftgate object sensors

3. Ignition ON, observe the scan tool Liftgate Secondary Obstacle Detection parameter. The reading should be between 3V-3.5V.

4. If not within the specified range, perform the Circuit/System Testing.

5. Observe the scan tool Liftgate Secondary Obstacle Detection parameter while pressing and releasing the B71R liftgate right-hand object sensor. The value should change from 3-3.5 V to 2.25-2.75 V when the sensor is pressed and released.

6. If the value does not change, test or replace the B71R liftgate object sensor - right.

7. Observe the scan tool Liftgate Secondary Obstacle Detection parameter while pressing and releasing the B71L liftgate left-hand object sensor. The value should change from 3-3.5 V to 2.25-2.75 V when the sensor is pressed and released.

8. If the value does not change, test or replace the B71L liftgate object sensor - left.


Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the B71L liftgate object sensor - left.

2. Test for less than 30 Ω between the low reference circuit terminal B and ground.

3. If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the K39 liftgate control module.

4. Disconnect the harness connector at the B71R liftgate object sensor - right

5. Ignition ON, test for 4.75-5.25 V between the signal circuit terminal A and ground.

6. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K39 liftgate control module.

7. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K39 liftgate control module.

8. Test for less than 10 Ω between the signal circuit terminal B at the B71R liftgate object sensor - right and the signal circuit terminal A at the B71L liftgate object sensor - left.

9. If greater than the specified range, test the signal circuit between the two sensors for an open/high resistance.

10. If all circuits test normal, test or replace the B71L liftgate object sensors.


Component Testing


1. Ignition OFF, disconnect the harness connectors at the B71 liftgate object sensor.

2. Test for 8k-12k Ω between the signal terminal A and the low reference terminal B.

3. If not within the specified range, replace the B71 liftgate object sensor.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.


Liftgate Side Upper Sensor Replacement

Control Module References for liftgate control module replacement, setup and programming