B275396 - Passenger sensor mat child seat detection, internal component fault airbag control unit fault

What does error code B275396 mean in the airbag control unit?

Error code B275396 reports that the automatic child seat detection of the sensor mat in the passenger seat is working incorrectly. There is an internal component fault. The airbag control unit stores the fault and switches on the airbag warning light.

The sensor mat on the passenger side also detects whether a child seat is fitted on the seat. If this detection fails, the airbag control unit cannot control the passenger airbag correctly.

Unlike the plain occupancy signal, this concerns the child seat detection. The fault type stands behind the basic code, and it shows that the component itself reports a fault internally.

How do you recognise error code B275396?

The airbag warning light stays on permanently, and B275396 is in the fault memory of the airbag control unit. It becomes visible with a diagnostic tool. The entry cannot be cleared permanently for as long as the child seat detection of the mat is not working properly.

The assignment is important: the entry concerns the child seat detection of the mat on the passenger side and not the airbags on the driver side.

What causes error code B275396?

Because the code names an internal component fault, the sensor mat itself is above all the likely defective part. Its connector, the wiring to the airbag control unit and the evaluation in the control unit are also possible causes.

• The sensor mat in the passenger seat has an internal defect.
• The connector of the mat is not properly connected.
• A wire to the mat is damaged.
• The airbag control unit evaluates the signal of the child seat detection incorrectly.

Which of these causes applies only becomes clear when a specialist workshop carries out an inspection. The connector and wiring are examined as well before the mat is established as the cause.

In which vehicles does error code B275396 occur?

Error code B275396 is known on the Mercedes-Benz SLK R172, a vehicle with a sensor mat and child seat detection on the passenger side. For other vehicles the meaning may differ, and the list is not complete.

Whether another Mercedes-Benz model with child seat detection on the passenger side shows the same entry is clarified by the fault memory once it has been read out.

How is error code B275396 resolved?

First have the fault memory read out with a diagnostic tool and have the connector and wiring of the seat occupancy detection checked in a specialist workshop. If the sensor mat itself is defective, Airbag24 offers a simulator for a defective seat occupancy mat.

Work on the airbag system belongs in expert hands. The specialist workshop checks the connector and the wiring and determines whether the mat is the cause.

If the cause is not the mat, connector or wiring but the airbag control unit itself, first disconnect the battery, remove the control unit, create a repair order online and send the unit to Airbag24. Checking, repairing and testing usually take 3–4 working days.

The simulator permanently sends the airbag control unit the same signal that an intact mat reports when the seat is occupied.

The simulator is intended exclusively for motorsport use and is not approved for public road traffic (StVO). With the simulator fitted, the passenger airbag deploys in an accident even when the seat is empty. A rear-facing child seat must therefore not be used on the front passenger seat.