B103315 airbag control unit fault

What does error code B103315 indicate in the airbag control unit?

Error code B103315 is a generic diagnostic trouble code (DTC) that points to a serious internal malfunction in the airbag control unit (SRS). The primary cause is typically an electronic fault on the circuit board, such as defective capacitors, resistors, or integrated circuits (ICs). This error compromises the proper functioning of the entire restraint system and results in the deactivation of the airbags.

Technically speaking, this error means that the control unit’s internal self-diagnostic has detected an anomaly, classifying it as non-operational. The unit can no longer reliably perform its monitoring and deployment functions, so it shuts itself down for safety reasons and activates the airbag warning light.

The malfunction may stem from faulty microcomponents responsible for data processing or power supply. Firmware errors or unerased crash data following an accident can also trigger this internal fault.

What symptoms are typical of error code B103315?

The most obvious symptom is a continuously illuminated or flashing airbag warning light on the instrument cluster. Often, the control unit is also inaccessible via diagnostic equipment, meaning no communication can be established. This is a clear indication of a severe internal defect that disables the entire airbag system.

The active airbag warning light serves as the primary alert for the driver, indicating that the Supplemental Restraint System (SRS) is inoperable and would not deploy airbags or pretensioners in the event of a crash.

Another common sign is complete loss of communication. Workshops can no longer access the control unit with their diagnostic tools to read fault codes or retrieve live data—the unit simply stops responding to CAN bus requests.

Even if communication initially remains sporadic, the persistent storage of error code B103315 is a key indicator that the root cause lies within the unit itself.

What technical causes lead to error B103315?

The main cause of B103315 is an electronic fault on the control unit’s circuit board, often due to failed ICs, capacitors, or resistors. Additional factors include stored crash data after an accident that locks the unit, as well as less frequent software glitches, overvoltage damage from jump-starts, or moisture ingress.

Defective electronic components are the most common source of failure. Aging, thermal stress, or vibrations can cause hairline cracks in solder joints or component failures on the board, disrupting internal operations.

Stored crash data is another typical culprit. After a collision, the control unit saves irreversible data that permanently locks it out. Even when no external damage is visible, the unit reports an internal fault.

Although less common, overvoltage damage—such as from an incorrectly connected battery or an unsuitable charger—can harm the sensitive electronics inside the control unit and result in this error code. The same applies to corrosion caused by water damage.

In which vehicles does error B103315 occur frequently?

Error code B103315 occurs most often in certain Audi models whose airbag control units feature a specific design and software version that are more susceptible to these defects. At Airbag24, we have identified this issue particularly in Audi S3 8V series models.

At Airbag24, we specialize in repairing airbag control units displaying error code B103315 for the following models:

Audi:

• S3 8V (model years 2013–2017)

• S3 8V Facelift (model years 2017–2020)

The prevalence of this error in these vehicles suggests a design-related vulnerability in a specific series of control units, which over time leads to this particular internal fault.

How does Airbag24 repair error B103315?

The repair focuses on eliminating the internal electronic fault. Upon receiving your removed control unit, Airbag24 analyzes it to pinpoint the source of the problem. Defective components on the circuit board are replaced, software issues are resolved, and any stored crash data is erased. A final test confirms full functionality before returning the unit with 2 years' statutory liability for defects.

The process at Airbag24 is designed for efficiency and precision. Once your control unit arrives, a comprehensive analysis is conducted using specialized equipment like oscilloscopes and multimeters to accurately identify the defect.

Subsequently, professional component-level repair is performed. Our technicians desolder defective components such as ICs or capacitors and replace them with high-quality new parts. If crash data is the cause, it is completely and securely erased from the control unit’s memory.

Each repaired control unit undergoes a final functional test on a dedicated test bench. This ensures that fault B103315 has been permanently resolved and that the device operates flawlessly once again. You receive 2 years' statutory liability for defects on the entire repair service.