Mercedes B009749 – Right-Hand Crash Sensor Fault
System: Safety System / Airbag System Component: Crash Sensor (Right-Hand Side) Part Reference: A54 (Right Side Air Bag Sensor)
Typical Symptoms
• Airbag warning light illuminated
• Message: “Restraint System Malfunction”
• Fault stored in airbag control unit
• Safety system warning displayed
Fault Codes
• B009749 – Crash sensor right-hand side malfunction (internal electrical fault)
Possible Cause
• faulty crash sensor (right-hand side)
• internal electrical failure of sensor
• wiring or connector issue
• sensor signal fault
Component Location
The crash sensor is typically located on the right-hand side of the vehicle, mounted within the body structure (e.g. front or side impact area depending on model).
Diagnostic Insight
Crash sensors are part of the airbag deployment system, detecting impact forces and sending signals to the control unit.
An internal electrical fault indicates the sensor is no longer operating correctly or providing valid data.
Technicians usually check:
• fault codes in the airbag control unit
• wiring and connector condition
• sensor communication and signal
In this case, the fault was traced to the right-hand crash sensor (A54), and replacement resolved the issue.
It is important to confirm the root cause before replacing components.
See Mercedes Fault Diagnosis Guide →
Important Note
Crash sensor faults may affect airbag system operation and deployment. These faults should not be ignored and must be properly diagnosed.
⚠ Professional Diagnostic Recommended
Airbag and safety system faults require specialist diagnostic equipment. The vehicle should be inspected by a Mercedes-Benz dealer or qualified Mercedes specialist.
