B2752 - Seat occupancy detection of the passenger sensor mat airbag control unit fault

What does error code B2752 mean in the airbag control unit?

Error code B2752 concerns the seat occupancy detection of the sensor mat in the passenger seat. The airbag control unit then receives no usable signal as to whether the passenger seat is occupied. It stores the fault in the fault memory and switches on the airbag warning light.

The sensor mat tells the airbag control unit whether the passenger seat is occupied. Without a valid signal, the control unit cannot control the passenger airbag correctly. The code applies to Mercedes-Benz and describes the basic fault at the seat occupancy mat on the passenger side.

Behind the basic code B2752, the fault memory also holds a fault type. It says more precisely what is being reported at the mat, for example an internal fault in the component.

How do you recognise error code B2752?

The airbag warning light stays on permanently, and the code B2752 is in the fault memory of the airbag control unit. It can only be read out with a diagnostic tool and returns after being cleared for as long as the cause at the seat occupancy detection remains.

• The airbag warning light in the instrument cluster stays on.
• A diagnostic tool shows the code B2752 together with the fault type in the fault memory.
• Clearing does not help permanently: the entry comes back.
• The diagnostic tool assigns the fault to the seat occupancy detection of the passenger seat.

What causes error code B2752?

Error code B2752 occurs when the signal of the seat occupancy detection is missing or incorrect. The possible causes are the sensor mat itself, its connector, the wiring to the airbag control unit or the evaluation in the airbag control unit.

• The sensor mat in the passenger seat has an internal defect.
• The connector of the seat occupancy detection is loose or has contact problems.
• A wire between the mat and the control unit is damaged or broken.
• The airbag control unit does not evaluate the signal of the mat correctly.

Which of these causes applies only becomes clear when a specialist workshop carries out an inspection.

In which vehicles does error code B2752 occur?

Error code B2752 is known on Mercedes-Benz, including the SLK R172 and the A-Class W176. For other vehicles the meaning may differ, and the list is not complete.

If your vehicle is not listed, the description here applies only with reservations. For Mercedes-Benz vehicles with seat occupancy detection on the passenger side, it is generally accurate.

How is error code B2752 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.

Do not work on the airbag system yourself: work on it belongs in expert hands. A specialist workshop reads out the fault memory, checks the connector and the wiring and determines whether the mat still delivers a signal.

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.

If the sensor mat itself is defective, 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.