B0118 airbag control unit fault

What does error code B0118 indicate in the airbag control unit?

Error code B0118 signifies a critical, internal hardware defect within the airbag control unit. Specifically, it points to electrical faults such as short circuits or open circuits directly in the unit’s electronics. This is not a software or communication issue but rather physical damage to components that requires professional repair.

Technically, this error means the control unit’s self-diagnostic system has detected a severe anomaly in its own electrical circuits. The unit determines that it can no longer reliably perform safety‑critical functions—such as monitoring sensors and activating airbags—and switches into a fault mode.

The root cause lies at the component level. Common culprits include capacitors, resistors, or circuit traces on the PCB that have been damaged by aging, thermal stress, or electrical influences. Without repairing these components, the entire airbag system remains inoperative.

What symptoms indicate error code B0118?

The primary symptom of error B0118 is a permanently or intermittently illuminated airbag warning light on the instrument cluster. In most cases, the entry stored in the fault memory cannot be cleared. In severe situations, communication with the control unit via a diagnostic tool may also become impossible.

The airbag warning light serves as a direct visual alert to the driver that there is an issue with the restraint system. With an internal hardware fault like B0118, this warning remains active because the fault is continuously detected by the control unit’s self‑diagnosis.

Another clear sign is the failure of attempts to clear the error. Workshops find that the error code reappears immediately, as the underlying physical cause—the defect on the circuit board—persists and cannot be resolved through a simple software reset.

If the internal electronics are severely damaged, the control unit’s communication processor may also be affected. The result is a complete loss of diagnostic capability, rendering the unit inaccessible to scan tools.

What technical causes lead to error code B0118?

The main cause of error code B0118 is an internal electronic fault within the airbag control unit itself. These are physical damages to electronic components, such as defective capacitors, resistors, or damaged circuits on the PCB. External factors like moisture or voltage fluctuations can exacerbate these defects.

Electronic components naturally age over time. Over years, thermal cycling and vehicle vibrations can lead to material fatigue and microscopic cracks in solder joints or components, resulting in open circuits or short circuits within the control unit.

Although the error code directly points to the control unit, a preliminary diagnosis at a specialized workshop is essential. This ensures that external issues—such as wiring problems or power supply malfunctions—are not mistakenly mistaken for an internal fault before the costly component is removed.

In which vehicles does error B0118 occur frequently?

Error code B0118 has been documented primarily in certain model series from Peugeot and Toyota. Affected models include the Peugeot Boxer, as well as various generations and variants of the Toyota Yaris, including the Yaris Cross and GR Yaris. Repair is often the most cost-effective solution in these cases.

At Airbag24, we have extensive experience repairing error B0118 and perform these repairs on the following specifically affected vehicle models:

Peugeot: Boxer III (2006–2011), Boxer III 1st Facelift (2011–2014), Boxer III 2nd Facelift (2014–2024), and Boxer III 3rd Facelift (2023–present).

Toyota: Yaris XP10 (1998–2003) and XP10 Facelift (2003–2006), Yaris XP130 (2010–2014) along with its facelift variants (2014–2020), Yaris XP150, Yaris XP210 (2020–present), Yaris Cross (2020–present), Yaris Sedan, Yaris Hatchback, Yaris GR (2020–present), and Vitz RS.

How is error B0118 repaired?

Professional repair begins with removing the faulty control unit and sending it to a specialist. There, a detailed electronic analysis is performed at the component level, defective parts are replaced, and a final functional test is conducted. Any stored crash data is also erased during this process.

After submitting the removed control unit to Airbag24, a standardized, quality‑assured repair process follows. Ideally, all relevant diagnostic logs should be included with the repair order to support the fault analysis.

In the first step, the control unit is opened and subjected to a comprehensive electronic analysis. Technicians identify the damaged components—whether capacitors, resistors, or circuit traces—and replace them with new, high-quality parts using proper procedures.

Following hardware repair, a full functional test is performed. If crash data from a previous accident is stored in the unit, it will also be completely and irreversibly erased during the repair process. The repaired control unit is then fully operational again.

The repair offers significant cost savings compared to purchasing a new part and eliminates the need for time-consuming reprogramming of the vehicle. All repairs come with 2 years' statutory liability for defects.