Airbag control unit with part number 9390579

What is the function of Airbag Control Unit 9390579?

The airbag control unit with part number 9390579 is the central control module for the occupant protection system (SRS/ACSM) in the BMW i8 I12. It processes data from crash sensors and is responsible for precisely and reliably deploying airbags and seatbelt pretensioners in the event of a collision, thereby protecting vehicle occupants.

As the brain of the passive safety system, this module continuously monitors all connected components of the restraint system. These include various airbags, seatbelt pretensioners, as well as acceleration and pressure sensors distributed throughout the vehicle that measure vehicle dynamics.

Its core function is to detect and evaluate an accident event within milliseconds based on sensor data. On the basis of this analysis, the control unit determines which restraint devices need to be deployed and at what intensity to ensure optimal protection.

Why does control unit 9390579 fail?

A major reason for failure of control unit 9390579 is stored crash data following an airbag deployment. This permanently blocks functionality and cannot be cleared using workshop diagnostic tools. Another common cause is internal electronic defects on the circuit board, such as issues with voltage regulators, microcontrollers, or memory chips (EEPROM).

After a crash in which airbags or seatbelt pretensioners have been activated, the control unit stores an indelible crash record. This is a manufacturer‑imposed safety feature that locks the module and prevents reuse without professional repair.

Even outside of a crash, hardware defects can occur on the circuit board. Faulty SMD components, corroded solder joints, or problems in the internal power supply often result in persistent error messages like “internal control unit error,” indicating a condition irreparable by conventional workshops.

How do you recognize a defect in control unit 9390579?

A defective airbag control unit 9390579 primarily manifests as a constantly illuminated or flashing airbag warning light on the instrument cluster. Often, communication between the diagnostic tool and the control unit also ceases. The fault memory contains permanent errors such as “internal error” or “crash data stored,” which cannot be erased.

The most obvious symptom is the airbag warning lamp in the cockpit. It remains lit after starting the vehicle, signaling a serious malfunction in the safety system that requires immediate inspection.

Another clear indication is when a specialized workshop cannot access the airbag control unit using a diagnostic device. Lack of communication points to a severe internal defect.

Error codes stored in the fault memory, such as “internal control unit error” or “component defective,” are also typical. These errors cannot be reset with standard diagnostic software and directly indicate a problem within the module itself.

In which vehicles is control unit 9390579 installed?

The airbag control unit with part number 9390579 was specifically developed for the BMW i8 and is used across two model generations. At Airbag24, we repair this control unit for the following specific vehicle models, restoring full functionality of the safety system and avoiding costly replacement purchases.

BMW i8 I12 Coupé (model years 2013–2018)

BMW i8 I12 LCI Coupé (model years 2018–2020)

How is control unit 9390579 repaired?

At Airbag24, repairs begin with a professional incoming inspection to precisely analyze the fault. Depending on the defect, stored crash data is irreversibly erased at the chip level, or faulty electronic components on the circuit board are replaced. Following restoration and a comprehensive functional test, the control unit is fully operational again. Each repair comes with 2 years' statutory liability for defects.

Upon receipt of the removed control unit, technicians perform diagnostics to verify the reported fault. They read the fault memory and visually inspect the circuit board for damage such as corrosion.

If a crash record is the cause, the memory chip (EEPROM) is directly read out and the lock is removed, logically resetting the module to its original state. For hardware defects, faulty SMD components are identified and replaced with new, high‑quality parts.

The original vehicle identification number and coding remain fully intact during the repair process. A final test on a dynamometer ensures that the control unit communicates flawlessly and functions perfectly before being returned to the customer.