B275200 - Passenger sensor mat seat occupancy detection, malfunction airbag control unit fault

What does error code B275200 mean in the airbag control unit?

Error code B275200 reports a malfunction of the seat occupancy detection at the sensor mat of the passenger seat. The airbag control unit then cannot reliably tell whether the seat is occupied, stores the fault and switches on the airbag warning light.

The seat occupancy mat on the passenger side supplies the airbag control unit with the information on whether the seat is occupied. If it is disturbed, the control unit cannot control the passenger airbag correctly.

With this code, the fault type follows the basic code, and it describes a general malfunction. It does not name a specific partial defect, so the exact cause has to be sought in the workshop.

How do you recognise error code B275200?

The fault shows up as a permanently lit airbag warning light. B275200 is read out of the fault memory with a diagnostic tool. The entry cannot be cleared permanently, because it returns for as long as the malfunction of the seat occupancy detection remains.

• The airbag warning light stays on after the engine is started.
• The diagnostic tool shows B275200 in the fault memory of the airbag control unit.
• After clearing, the entry appears again.

What causes error code B275200?

A malfunction of the seat occupancy detection can lie in the sensor mat, its connector, the wiring or the airbag control unit. Which part is affected can only be clarified by checking the individual components.

• The sensor mat in the passenger seat no longer works properly.
• There is a contact fault at the connector.
• A wire between the mat and the control unit is broken or damaged.
• The airbag control unit does not receive or evaluate the signal correctly.

In which vehicles does error code B275200 occur?

Error code B275200 is known on Mercedes-Benz, namely on the A-Class W176 and the SLK R172. For other vehicles the meaning may differ, and the list is not complete.

Other Mercedes-Benz models with seat occupancy detection on the passenger side may show the same entry. This can only be confirmed once the fault memory has been read out, because the meaning may differ from vehicle to vehicle.

How is error code B275200 resolved?

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

Do not touch the airbag system yourself, because work on it belongs in expert hands. The workshop checks the connector and the wiring and tests whether the mat is still working.

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.