What does the error code B1BC749 indicate?
The error code B1BC749 indicates a critical internal electrical fault in the airbag control unit (SRS). This points to a hardware defect in the internal electronics, for example, in the memory chips. As a result, the entire airbag system is deactivated for safety reasons, which poses a significant safety risk.
In technical terms, the code "B1BC7-49: Internal Electronic Failure" means that the control unit has detected an implausible function in one of its own components. It can no longer reliably perform its monitoring and triggering functions and therefore shuts down.
The activation of the SRS warning light is the direct result of this self-test, to alert the driver to the failure of the restraint system.
How can you identify error B1BC749?
The most obvious symptom of fault code B1BC749 is a continuously illuminated or flashing SRS airbag warning light in the instrument cluster. Often, it is also no longer possible to access the airbag control unit with a diagnostic tool due to communication problems. In this state, the airbags are completely deactivated.
The warning light does not go out after the vehicle is started, which indicates a permanent and not just sporadic fault.
Another sign could be that the fault suddenly occurs after a battery change, a deep discharge, or after adjusting the front seats. The latter could indicate a previously damaged control unit or additional problems with the wiring under the seats.
What are the causes of B1BC749?
The primary cause of error code B1BC749 is an internal hardware electronics defect in the control unit, such as faulty memory chips or damaged solder joints. Other triggers can include stored crash data after an accident, overvoltage in the vehicle's electrical system, or age-related component fatigue.
The most serious cause is an internal electronic defect, as this can lead to microprocessors or memory modules losing their function. Simply clearing the error memory is not possible in this case, since the hardware damage persists.
Even if an accident occurs without airbag deployment, crash data can be stored in the control unit, leading to a permanent lockout. Similarly, cold-induced cable breaks or moisture can damage the sensitive electronics.
Before sending the control unit in for repair, external sources of error such as defective connectors under the seats (often yellow 2- or 4-pin connectors), a faulty seat recognition mat or a defective seat belt buckle should be ruled out.
Which vehicles are affected by the error code B1BC749?
The error code B1BC749 primarily occurs in Mercedes-Benz C-Class models from model years 2014 to 2023. It has also been diagnosed in some older Peugeot models. Repairing the original control unit is the most reliable solution in these cases.
At Airbag24, we repair control units with the error code B1BC749 for, among others, the following specific vehicle models:
Mercedes-Benz C-Class S205 T-Model (model years 2014-2021)
Mercedes-Benz C-Class A205 Cabriolet (model years 2016-2023)
Peugeot 205 I
Control units with part numbers such as A2C81768406 or A2C92704000 are often affected. The repair restores the full functionality of these specific components.
How is error B1BC749 professionally repaired?
Professional repair of error code B1BC749 focuses on repairing the internal hardware of the control unit. After being sent to Airbag24, the unit is analyzed, defective electronic components such as memory chips are replaced, and any existing crash data is completely erased. This restores full functionality.
A repair is far more than just clearing the fault memory. It is a cost-effective and sustainable alternative to an expensive new purchase, which is often associated with complex coding at the authorized dealership.
Upon arrival at Airbag24, the control unit undergoes a comprehensive diagnostic check at the component level. Our technicians identify the exact source of the fault on the circuit board, replace defective components with new, high-quality parts, and perform reprogramming to ensure full compatibility with the vehicle.
Final functional tests ensure that the control unit is working perfectly again. Repairing the original unit preserves the original vehicle coding, so it is usually ready for operation immediately after installation.
We offer a 12-month warranty on all repairs to ensure the longevity and reliability of the repair.
