B1640 airbag control unit fault

What does error code B1640 mean?

Error code B1640 indicates a specific malfunction or internal defect in the airbag control unit. This error points to a problem with the module’s hardware electronics, which impairs the proper functioning of the safety system and typically cannot be resolved simply by clearing the fault memory.

Technically speaking, it is a documented fault condition where the control unit detects an internal anomaly. This may affect sensor signal processing or the airbags’ deployment logic. The system then switches to a safety mode to prevent false activations, which is indicated by the activation of the airbag warning light.

How can you recognize error B1640?

The primary and most obvious symptom of error B1640 is a continuously illuminated or intermittently flashing airbag warning light on the instrument cluster. Often, the control unit can no longer be accessed with a diagnostic tool, making further fault analysis at the workshop impossible.

The airbag warning light usually remains active even after restarting the engine. This is a clear indication that a permanent, safety‑related fault exists in the system, requiring immediate inspection.

In many cases, communication between the scan tool and the airbag control unit completely fails. The module does not respond to diagnostic requests, preventing the internal fault stored in the control unit from being read out or cleared.

Another possible symptom suggesting a defect in the control unit is crash data retained after an accident. These data block normal operation of the device and often cannot be removed using standard workshop testers.

What causes B1640?

The main cause of error code B1640 is an internal electronic defect within the airbag control unit itself. Frequently, this results from crash data stored after an accident that locks the unit, or from component damage caused by overvoltage in the vehicle’s electrical system.

After a collision, so‑called crash data are permanently recorded in the control unit’s memory. These data often cannot be erased with conventional diagnostic tools, leading to persistent error codes like B1640, as the control unit is considered “worn out.”

Electrical faults in the vehicle—such as voltage spikes caused by a defective alternator or jump-starting with incorrect polarity—can result in overvoltage damage to the sensitive electronic components inside the control unit.

Communication issues between the control unit and connected sensors or other system components may also contribute, although error code B1640 primarily points to a defect within the control unit itself.

Which vehicles experience error B1640?

Error code B1640 has been documented across several manufacturers, particularly in models from Opel, Citroën, and Toyota. Vehicles from premium brands such as Bentley, Lamborghini, and Lexus can also be affected by this specific control unit fault.

At Airbag24, we repair error code B1640 for a wide range of models, including:

Bentley: Bentayga Speed Mk1

Citroën: C4 VTS I

Dacia: Nova I (1995–2000), 1304 I

Lamborghini: Huracán LP580-2 (2015–2020)

Lexus: RZ BZ4X (from 2023)

Opel: Crossland X (2017–2024)

Toyota: 4Runner TRD Pro, Crown Hybrid, GT86 (ZN6, ZN6 Facelift), Hyryder G16E, Pixis Truck, Previa XR50, Sienna (XL30, Woodland Edition)

How is error B1640 professionally repaired?

A professional repair of error B1640 requires detailed component‑level analysis. After removing and sending in the control unit, a precise diagnosis is performed to pinpoint the root cause. Defective components are then repaired or replaced, and any stored crash data are cleared.

The process at Airbag24 begins with an initial inspection of the submitted control unit. Our technicians analyze the electronics to identify the exact cause of error B1640—whether it’s a hardware defect or locked data.

The next step involves actual electronic repair, which may include erasing crash data, repairing circuit traces, or replacing faulty microchips. The goal is to restore the original device to full functionality.

Finally, the control unit is recalibrated and undergoes rigorous functional testing to ensure that error B1640 has been resolved and that the module communicates flawlessly once again. We provide 2 years' statutory liability for defects on all repairs.