B0137 airbag control unit fault

What does error code B0137 mean?

Error code B0137 indicates a performance issue in the active aerodynamics system, monitored by the airbag control unit. Contrary to popular belief, this is not a typical airbag-related fault such as stored crash data; rather, it points to a malfunction in a position sensor that controls, for example, an active spoiler or an air flap. The control unit detects implausible signals and sets the error code.

Technically speaking, code B0137 describes a “performance problem” with position sensor ‘A’ for active aerodynamic feature ‘D’. This means the values reported by the sensor fall outside the manufacturer-defined nominal range. In this case, the airbag control unit (SRS – Supplemental Restraint System) is not only responsible for occupant safety but also monitors systems that affect vehicle stability.

Although the fault does not directly indicate a problem with an airbag or seatbelt pretensioner, the airbag warning light illuminates because the overarching safety system has detected an issue in one of its monitored components. The integrity of the entire system can no longer be guaranteed, prompting a warning to the driver.

How do you recognize error code B0137?

The primary symptom of error code B0137 is a permanently illuminated airbag warning light on the instrument cluster. Additionally, malfunctions may occur in the active aerodynamics system, such as a spoiler that fails to extend or air flaps that remain stuck. In some cases, a specific warning message appears on the display.

The airbag warning light remains on after starting the vehicle and does not extinguish as usual following the system check. This is a clear indication that an active fault is stored in the SRS control unit’s fault memory.

Another sign is functional impairment of the aerodynamics component itself. Depending on the vehicle model, this could mean that a rear spoiler no longer deploys based on speed or that radiator flaps remain locked in one position. Such issues can affect driving stability at high speeds or engine cooling.

During the main inspection (TÜV/HU), a lit airbag warning light inevitably results in a significant defect, leading to refusal of the inspection sticker. Repair is therefore mandatory.

What causes error code B0137?

The most common cause of error code B0137 is a defective or mechanically damaged position sensor in the aerodynamics system. Other reasons include wiring problems such as broken cables or corroded connectors. Less frequently, the fault lies within the airbag control unit itself, due to internal hardware damage or software issues.

The position sensor should be considered the primary source of the problem. Contamination, mechanical damage, or internal wear can cause it to report implausible values. A visual inspection of the sensor and its mechanics is often the first diagnostic step.

The electrical connection between the sensor and the control unit is also a frequent weak point. Pinched or broken cables, along with corroded contacts at the connectors, can distort or completely disrupt the sensor signal.

In rarer cases, an internal defect within the airbag control unit itself may be responsible. This can result from water damage, short circuits, or faulty components on the circuit board. Software or firmware errors in the control unit can likewise lead to misdiagnosis of the sensor.

Error code B0137 is often accompanied by related codes such as B0138, B0139, or B013A, which point to additional issues within the same system and must be taken into account during diagnosis.

In which vehicles does error code B0137 occur?

Error code B0137 specifically affects certain models from Citroën and Land Rover. These include the Citroën Relay of the first and second generations, as well as the Land Rover Freelander 1, including the facelifted version. At Airbag24, we specialize in repairing the relevant control units for these vehicles.

At Airbag24, we repair control units displaying error code B0137 for the following models:

Citroën: Relay I (model years 1994–2002) and Relay II (model years 2001–2006).

Land Rover: Freelander 1 (model years 1997–2003) and Freelander 1 Facelift (model years 2003–2006).

It is important to note that this error code may have a completely different meaning when applied to other manufacturers such as BMW, VW, or Mercedes. The causes and solutions described here apply exclusively to the aforementioned models.

How is error code B0137 professionally repaired?

Professional repair begins with a thorough vehicle diagnosis to precisely locate the source of the fault. After sending the removed airbag control unit to Airbag24, an electronic analysis is performed, defective components are replaced, and the software is checked. Finally, a functional test ensures full operability.

First, a thorough diagnosis should be performed in the workshop. This includes reading all fault codes, visually inspecting sensors and wiring, as well as conducting electrical measurements of voltage and resistance to clearly identify the source of the problem.

If an internal control unit defect is confirmed, the unit is removed and sent to Airbag24. Our technicians carry out a detailed component-level analysis to pinpoint the exact cause. Defective components are professionally replaced, and solder joints are reworked.

Next, the device’s software is checked and updated if necessary. Any existing old fault codes are cleared. Following repair, each control unit undergoes a comprehensive functional test on a specialized test bench.

The repair offers a plug-and-play solution, as the original vehicle coding is preserved. Therefore, time-consuming reprogramming in the vehicle is not required. We provide 2 years' statutory liability for defects on all repairs.

Is Repairing the Control Unit Worth It?

Repairing the airbag control unit is an economically and technically sensible alternative to the costly purchase of a new one. You often save significantly compared to a new part, which can cost several hundred euros. Additionally, complex reprogramming in the vehicle is unnecessary, saving both time and further workshop expenses.

The biggest advantage is the substantial cost savings—up to 70% compared to a new OEM part. You receive a fully functional component at a fraction of the new price.

Since the original control unit is repaired, all vehicle-specific data, such as the VIN and coding, remain intact. After repair, the unit can be easily reinstalled and will function immediately without expensive relearning at an authorized service center.

Moreover, this repair is a sustainable solution, as valuable electronic components are reused. With 2 years’ statutory liability for defects on the work performed, you gain added assurance and invest in a durable, reliable repair.