FC:240 Interner Fehler (Steuergerät defekt) airbag control unit fault

What does error code 240 mean in the airbag control unit?

Error code 240 (also known as F0 240) indicates a serious internal fault in the airbag control unit. This error points to electronic damage or permanent locking of the unit, often caused by stored crash data. Communication with the control unit is usually no longer possible, and the error cannot be cleared using standard workshop diagnostic tools.

Technically speaking, this means that the control unit’s internal self-diagnosis has detected an irreparable hardware or data integrity failure. The system classifies itself as unreliable and enters a safety mode, signaled by the permanently illuminated warning light.

Due to the electronically damaged or locked condition, diagnostic tools such as ISTA or INPA cannot simply reset the error. The fault lies not at the software level, which could be erased, but deep within the hardware or the unit’s permanent memory.

How can you recognize error code 240?

The main symptom of error 240 is the permanently lit airbag warning light on the instrument cluster. Additionally, a stable diagnostic connection to the airbag control unit often cannot be established, or communication breaks down. Attempts to clear the fault memory fail, and the warning light remains constantly active.

The airbag warning light stays on immediately after the engine starts and does not go out as it normally would. This is a clear indication of a critical, permanent fault in the safety system.

Another typical sign is the loss of communication during vehicle diagnostics. When a diagnostic tool is connected, it frequently reports “No communication possible” or fails to establish a connection with the airbag module. This confirms that the control unit itself is the source of the problem.

Even if a temporary connection is established, error code 240 cannot be erased from memory. The command is ignored or rejected by the control unit because the underlying cause is a physical or data-related defect.

What causes error code 240?

The most common cause of error code 240 is an internal electronic fault on the control unit’s circuit board or the storage of crash data following an accident. Other triggers may include voltage issues, short circuits in the power supply, incorrect coding, or environmental factors such as moisture ingress that lead to hardware damage.

Internal electronic faults are a major cause. These include damage to the circuit board, cold solder joints, or failure of critical components like processors and memory chips (EEPROM), which are essential for the control unit’s operation.

After an accident, crash data is permanently stored in the control unit’s memory. For safety reasons, this data locks the unit and cannot be deleted through normal OBD diagnostics. The control unit must be electronically reset.

Incorrect coding or programming—such as when attempting to reprogram a used control unit—can also trigger an internal conflict and result in error 240.

Voltage problems in the vehicle’s electrical system, such as overvoltage from jump-starts or repeated undervoltage, can permanently damage the sensitive electronics of the airbag control unit. Similarly, external short circuits or moisture damage can contribute to this fault pattern.

Which vehicles are affected by error code 240?

Error code 240 primarily occurs across a wide range of BMW, MINI, and Rover models. Affected series include various generations such as the BMW 3 Series (E36, E46), 5 Series (E34, E39), and 7 Series (E23, F04), as well as different MINI Cooper and One generations. Airbag24 specializes in repairing these specific control units.

At Airbag24, we repair error code 240 for numerous vehicles, particularly the following models:

BMW: 1 Series F40 (2019–2024), 3 Series E36 (1990–2000), 3 Series E36/2C Cabrio (1993–1999), 3 Series E46 (1998–2007) including Coupe, Touring, and Compact variants, 5 Series E28 (1981–1987), 5 Series E34 (1988–1996), 5 Series E39 (1995–2004), 6 Series E24, 7 Series E23 (1977–1986), 7 Series F04 ActiveHybrid (2010–2015), 7 Series G70 (2022–present), 8 Series E31 (1989–1999), Z3 E36/7 Roadster (1995–2002), Z3 E36/8 Coupé (1995–2002), and M3 E46 (2000–2006).

MINI: Mini Mk VII, Cooper R56, Cooper S R56, Cooper D R56, Cooper SD R56, One R50, One R56, One F56, Cooper Convertible R52, and Coupe R58.

Rover: Mini Cooper, Mini Cooper S, Mini One, and Mini Spark.

How is error code 240 professionally repaired?

Professional repair of error 240 involves sending in the removed airbag control unit. At Airbag24, the unit first undergoes a thorough electronic analysis. Stored crash data is then erased, defective components on the circuit board are replaced, and the unit is restored to factory settings, making it fully functional again.

The process begins with the proper removal of the control unit from the vehicle. Before removing the unit, ensure that external sources of fault—such as wiring or fuses—have already been inspected.

Upon submission to Airbag24, our technicians perform a thorough individual diagnosis to pinpoint the exact cause of the internal error. During this step, the entire circuit board is examined for electronic damage.

The central repair procedure involves erasing the crash data and repairing the hardware. Defective components, such as memory chips or processors, are replaced. This restores the control unit to its original factory condition and removes the internal lockout.

Following successful repair, the control unit is typically “Plug & Play” ready. It can be reinstalled directly into the vehicle without requiring time-consuming re-coding at an authorized dealer. We provide a 12-month warranty on all repairs.