B1305 airbag control unit fault

What does error code B1305 indicate in the airbag control unit?

Error code B1305 points to a serious internal fault in the airbag control unit, primarily occurring in Mitsubishi models. The root cause is usually hardware defects on the circuit board, such as faulty microcontrollers or capacitors, triggered by aging, overvoltage, or stored crash data.

Technically speaking, code B1305 signals that the control unit’s self-diagnosis has detected an irreparable internal error. As a result, the entire airbag system is preemptively deactivated to prevent false activations. Consequently, the airbags can no longer function reliably.

The fault is often so severe that the device’s central processing unit (microcontroller) becomes locked. This explains why communication via the diagnostic interface is frequently impossible. The control unit enters a safe but inactive state.

How do you recognize error B1305?

The main symptom of error B1305 is a continuously illuminated airbag warning light on the instrument cluster. Additionally, it is often impossible to access the airbag control unit with a diagnostic tool, as communication is blocked by the internal fault.

The airbag warning light illuminates immediately upon ignition and remains on. This is a clear indication that the system has detected a critical error and is not operational.

Another typical sign is complete loss of communication. When a workshop attempts to read the fault memory, the diagnostic tool reports that no connection can be established with the airbag control unit.

Why does error code B1305 occur?

The most common cause of B1305 is an internal electronic malfunction, often triggered by crash data stored after an accident, which locks the unit. Overvoltage in the vehicle’s electrical system or age-related wear of components such as microcontrollers and capacitors also contribute to this hardware failure.

An internal control unit defect is the primary cause. Following a collision, so‑called crash data are permanently stored in the control unit’s memory. These data disrupt normal operation and must be professionally erased to restore functionality.

Voltage spikes—caused, for example, by a weak battery or jump-starting—can damage sensitive electronic components on the circuit board. Similarly, the natural aging of electronics over time leads to material fatigue and component failures.

Error code B1305 shares similarities with other internal fault codes, such as B1B05. In VW models, similar coding (B1304/B1305) may indicate an unconfigured seatbelt pretensioner control unit, highlighting the complexity of diagnosis. General errors like 65535 (control unit defective) or P0560 (system voltage) can also appear in related contexts.

Which vehicles are affected by B1305?

Error code B1305 occurs predominantly in various Mitsubishi models. Specifically affected are the Pajero Sport, Lancer, L200, Mirage, and Xpander Cross. Airbag24 offers professional repair services for these and other vehicles.

At Airbag24, error code B1305 is repaired for the following specific Mitsubishi models and series:

Mitsubishi Lancer CZ and Mitsubishi Lancer Evolution VI

Mitsubishi L200, model series K74 and KJ (2015–2023)

Mitsubishi Mirage CA and Mitsubishi Xpander Cross A05A

Mitsubishi Pajero Sport K90 (model years 1996–2008)

How is error code B1305 professionally repaired?

Repairing error B1305 requires component-level restoration. After sending the unit to Airbag24, the control unit is opened, defective electronic parts such as microcontrollers or capacitors are replaced, stored crash data is erased, and the device is thoroughly tested for full functionality.

The repair process at Airbag24 begins with a detailed analysis of the circuit board. Technicians identify the damaged components responsible for the internal fault.

These defective components are then carefully desoldered and replaced with new, high-quality parts. This may include circuits damaged by overvoltage or the central microcontroller. A crucial step is resetting the memory, particularly erasing crash data that locks the unit.

Following repair, the control unit undergoes comprehensive functional testing to ensure seamless communication with the vehicle and proper execution of all safety functions. We provide 2 years' statutory liability for defects on all repairs performed.