B0105 airbag control unit fault

What does error code B0105 in the airbag control unit indicate?

Error code B0105 is a specific diagnostic code that signals a fault in the airbag system, directly detected by the control unit (ACU). It points to a malfunction whose cause can range from external components—such as defective sensors, cables, or connectors—to internal electronic faults within the module itself, for example due to moisture damage or stored crash data.

This error code indicates that the airbag control unit has detected an irregularity that compromises the safe operation of the restraint system. The system then switches to a safety mode to prevent unintended deployment. The airbag warning light illuminates to alert the driver.

Electronically, this means either an input signal from a sensor is outside tolerance, an internal component within the control unit itself is faulty, or—very often—the so‑called crash data remains stored in the module’s memory after an accident. Such data permanently locks the control unit and must be professionally cleared to restore functionality.

How do you recognize error B0105?

The primary and unmistakable symptom of error B0105 is the continuously illuminated airbag warning light on the instrument cluster. This clearly warns the driver of a malfunction in the safety system. Consequently, proper airbag deployment in the event of a crash can no longer be guaranteed.

The warning light typically stays on immediately after starting the engine and does not extinguish as usual following the system’s self‑test. This is a clear indication that a significant fault is recorded in the airbag system’s error memory, requiring prompt diagnosis.

Other symptoms are usually not directly visible to the driver. However, the critical consequence is that the entire passive safety system may be disabled, which could have severe repercussions in the event of an accident.

What causes B0105?

The main causes of error code B0105 are varied and require systematic inspection. Often, it is stored crash data following an accident that blocks the control unit. Additional reasons include physical defects in sensors, damaged cables or corroded connectors, as well as internal electronic damage within the control unit itself, such as moisture ingress.

One of the most common causes is stored crash data. After an airbag deployment, the control unit enters a so‑called “consumption state,” becoming internally locked and requiring either replacement or professional data clearing to restore functionality.

External electrical issues are also a frequent source. These include short circuits, defective impact sensors, a damaged coil spring in the steering column, or loose connectors. A careful visual inspection of wiring and connected components is therefore an essential first step in diagnosis.

Internal defects within the control unit itself can also trigger B0105. Moisture damage leading to corrosion on the circuit board, cold solder joints, or failure of individual electronic components are among the possible causes.

In which vehicles does error B0105 occur?

Error code B0105 occurs across brands, as many manufacturers rely on similar electronic system components. At Airbag24, we repair this fault for models from Daewoo, Jaguar, Land Rover, Lexus, Porsche, Seat, SsangYong, and Toyota, underscoring the widespread prevalence of this issue.

Specifically, we have experience repairing this fault in the following models:

Daewoo: Matiz (M200)

Jaguar: XE S (X760)

Land Rover: Defender (L663, model years 2020–2025)

Lexus: LS (XF30, model years 2000–2006, including facelifts)

Porsche: Boxster Spyder (981)

Seat: Leon Cupra (Mk3) and Formentor (Mk1)

SsangYong: Torres (KR10, from model year 2022 onward)

Toyota: 4Runner (N280, model years 2009–2024, including both facelifts)

How is error B0105 repaired?

Professional repair of error B0105 involves complex electronic restoration. At Airbag24, the removed control unit is analyzed upon receipt to pinpoint the exact cause. Subsequently, electronic faults are corrected, components replaced, and—most importantly—the stored crash or system errors erased before a final functional test ensures full operational readiness.

The process ideally begins with a vehicle diagnosis to rule out external sources of failure, such as cables or sensors. Once the root cause is identified within the control unit, it is removed and sent in for repair.

Upon receipt at Airbag24, a detailed analysis is performed using specialized equipment. Our technicians address any identified electronic faults, which may involve replacing damaged components, cleaning contacts, repairing circuit traces, or eliminating moisture-related damage. The most critical step is the proper erasure of crash data that has locked the module.

Following successful repair, the control unit undergoes a comprehensive functional test. Only when all parameters are correct is the module returned. After reinstallation in the vehicle, the airbag warning light must illuminate and then extinguish. We provide a 12-month warranty on all repairs.