B1805 airbag control unit fault

What does error code B1805 mean?

Error code B1805 indicates a critical internal short circuit in the passenger-side airbag squib circuit. The airbag control unit detects this hardware fault through its self-diagnosis directly on the circuit board and permanently stores it in the fault memory, resulting in deactivation of the affected airbag system.

Technically speaking, this means there is a faulty electrical connection within the passenger-side airbag deployment circuit. The control unit measures a resistance value outside the predefined tolerance, indicating a short circuit. This condition prevents safe and controlled airbag deployment in the event of a crash.

The control unit’s self-diagnosis is a key safety feature, continuously monitoring all relevant circuits and components. Once a critical fault such as B1805 is detected, the airbag warning light illuminates to alert the driver.

How can you recognize error B1805?

The primary and unmistakable symptom of error code B1805 is the persistent illumination of the airbag warning light on the instrument cluster. This signals a serious malfunction that compromises the occupant protection system and requires immediate inspection.

After starting the vehicle, the airbag control unit performs a self-test. If error B1805 persists, the warning light remains on and does not extinguish after a few seconds, as it normally would during normal operation. Other functional impairments during driving typically do not occur; however, safety in the event of a collision is no longer guaranteed.

When reading the fault memory with a professional OBD2 diagnostic tool, code B1805 appears as an active or permanently stored fault. Simply clearing the fault is usually not possible, as the underlying hardware issue remains unresolved.

What causes B1805?

The main cause of error code B1805 is an internal short circuit directly within the airbag control unit. However, external factors such as defective cables, water ingress into the control unit, overvoltage damage, or poor connector contacts can also trigger or exacerbate this internal defect.

A common trigger is water damage. Moisture entering the control unit housing leads to corrosion and short circuits on the circuit board, affecting the passenger-side airbag ignition circuit.

Overvoltage—such as from jump-starting or issues in the vehicle’s electrical system—can also damage sensitive electronic components inside the control unit, resulting in internal faults like B1805.

In rarer cases, damaged wiring harnesses or corroded connectors near the control unit may distort measurement readings. A thorough visual inspection of wiring and connectors is therefore part of the professional diagnosis.

Which models experience error B1805?

Error code B1805 primarily occurs in a wide range of Toyota vehicles. Affected are various model series and types, including sedans, SUVs, and commercial vehicles equipped with specific generations of airbag control units.

At Airbag24, we professionally repair error code B1805 for the following Toyota models:

Toyota: Corolla Wagon, Corolla Cross, Camry Hybrid, Avalon TRD, Crown Royal, Aqua Cross, Highlander XU70 (from 2019), Estima XR40 (2000–2006), Estima XR50 (2006–2019), HiAce Commuter, Innova Crysta, Fortuner AN50 (2005–2015), Etios Liva (2011–2023), and Porte NNP10.

How is error B1805 professionally repaired?

Professional repair of error B1805 focuses on eliminating the internal short circuit on the airbag control unit’s circuit board. After submission, the device is analyzed, the defect is fixed at the component level, and then the fault memory—including any crash data—is cleared.

Following removal of the control unit from the vehicle by a specialized workshop, it is sent in for repair. At Airbag24, repairs follow a standardized process. First, an initial inspection verifies the reported fault.

Next, skilled technicians address the short circuit in the passenger-side airbag ignition circuit by replacing defective electronic components on the circuit board. Upon successful repair, the fault memory is completely erased. If the vehicle was involved in a crash, any permanently stored crash data is also reset.

Final tests ensure the control unit is fully functional again. The repaired unit can then be reinstalled in the vehicle (plug-and-play). All repairs come with 2 years' statutory liability for defects.