B137A airbag control unit fault

What does error code B137A mean in the airbag control unit?

Error code B137A indicates a critical signal loss in the airbag system (SRS). Technically, this means the control unit is not receiving a valid signal from an essential sensor, wiring harness, or internal component. As a result, the affected airbag circuit is deactivated, and the warning light illuminates.

When error B137A occurs, the SRS control unit detects an interruption or an implausible value in one of its monitoring circuits. The system can no longer guarantee that the airbags or seatbelt pretensioners will deploy correctly in the event of a crash. For safety reasons, a fault is therefore reported.

The cause may lie externally, in the peripheral components of the control unit—such as wiring or sensors—or internally, due to a defect on the control unit’s circuit board itself. Precise diagnosis is essential to pinpoint the exact source of the problem.

How do you recognize error B137A?

The primary and unmistakable symptom of error code B137A is the continuously illuminated airbag warning light on the instrument panel. Often, diagnostic equipment also shows no communication or only limited communication with the airbag control unit, complicating troubleshooting.

The airbag warning light typically illuminates immediately after starting the vehicle and remains on. This is a clear indication that the vehicle’s self-diagnostic system has detected a serious fault in the safety system.

When attempting to read the fault memory with an OBD2 scanner, code B137A appears. In some cases, however, the control unit may be completely unresponsive, suggesting a more severe internal failure, sometimes accompanied by additional error code B1000 (no communication).

Depending on the underlying cause, other error codes may also be logged. Codes such as B1007 (resistance too low) or B101A (open circuit/short circuit to positive) provide more specific clues about the affected component, such as a seatbelt pretensioner or a crash sensor.

What causes B137A?

The causes of error code B137A are varied, ranging from simple connection issues to complex internal hardware defects. Common culprits include breaks or shorts in the wiring, faulty sensors, corroded connectors, or a defect on the control unit’s circuit board itself.

A major cause is physical damage to the wiring. A broken wire or short circuit to a sensor—such as the front‑mounted crash sensors or seatbelt pretensioner sensors—directly results in signal loss.

Connectors are another frequent weak point. Especially in vehicles with frequently adjusted front seats or in three‑door models, cable connections beneath the seats can suffer. Moisture‑induced corrosion further exacerbates this issue.

A specific cause affecting the driver’s airbag is a defect in the slip ring behind the steering wheel. This component provides electrical connectivity to the steering wheel and can wear out due to constant rotational movement.

Not infrequently, the root cause lies directly within the airbag control unit. An internal fault triggered by defective parts—such as capacitors, resistors, or ICs on the circuit board—can produce error B137A. This is sometimes accompanied by the general error code 65535 (control unit defective).

In which models does error B137A occur?

Error code B137A is specifically diagnosed in Bentley models, particularly the Bentley S1 Standard. Since control unit technologies are often shared across platforms, this fault may also appear in select VW, Audi, Seat, and Skoda vehicles.

At Airbag24, we repair error code B137A for the following specifically affected models and brands, provided they are equipped with compatible control units:

Bentley: S1 Standard

Volkswagen, Audi, Seat, Skoda: Various models featuring platform‑compatible airbag control units. The extent of the issue depends heavily on the model year and the specific vehicle platform.

How is error B137A professionally repaired?

Professional repair of error B137A requires removing the airbag control unit and sending it to a specialized service center. There, a thorough analysis at the component level is performed, defective electronic parts are repaired, fault and crash data are cleared, and a final functional test is conducted.

After submitting the removed control unit to Airbag24, the repair process begins with an in-depth diagnosis. Our technicians inspect the circuit board for visible damage and conduct electronic measurements to identify the precise source of the fault.

In the next step, the defective components on the circuit board are professionally replaced. This may involve replacing resistors, capacitors, processors, or other integrated circuits (ICs) to restore full functionality.

Subsequently, all stored fault codes—especially code B137A—as well as any crash data present in the control unit’s memory are erased, returning the device to its factory‑default state.

Finally, the repaired control unit undergoes comprehensive functional testing to ensure it operates flawlessly once again. We provide 2 years’ statutory liability for defects on the repair performed.