B1505 airbag control unit fault

What does error code B1505 mean in the airbag control unit?

Error code B1505 indicates an internal diagnostic fault in the airbag control unit, classified as “self-test failed.” This means that the control unit’s self-diagnosis has detected a serious malfunction in its own internal circuitry or memory components. The system can no longer guarantee its proper operation and preemptively illuminates the airbag warning light.

Technically, the airbag control unit performs a self-test during each ignition cycle to verify the integrity of all connected components, such as sensors, ignition circuits, and internal wiring. If this self-test fails, DTC B1505 is stored in the fault memory.

This error suggests that the control unit has deemed itself unreliable. Consequently, it is unable to process correct signals from crash sensors in the event of an accident and properly deploy restraint systems like airbags and seatbelt pretensioners.

What symptoms indicate error B1505?

A stored B1505 code manifests through clear, safety‑related symptoms. The primary sign is a permanently illuminated or flashing airbag warning light on the instrument cluster. Additionally, communication issues with the control unit may occur, and the fault often cannot be cleared permanently.

The most noticeable symptom is the activated airbag warning light, which remains on after starting the vehicle—indicating an active, stored fault in the safety system.

In many cases, with an active B1505 fault, communication between the diagnostic tool and the airbag control unit is either absent or faulty. Diagnostic requests via the OBD interface remain unanswered or are interrupted.

Another clear indication is that the B1505 error code cannot be erased from the fault memory using conventional diagnostic tools. Even if temporary clearing appears successful, the fault reappears immediately during the next self-test.

What causes error code B1505?

The causes of B1505 are varied, ranging from external influences to internal hardware defects within the control unit itself. Common culprits include poor electrical connections, cable breaks, or corrosion. Once these external factors are ruled out, the defect usually lies in the control unit’s internal electronics—such as faulty memory chips or the diagnostic circuitry.

Before attributing the issue to the control unit itself, external sources must be inspected. These include loose connectors or defective airbag plugs, which tend to wear out due to constant seat movement, especially in three-door vehicles.

Broken or crushed cables, corrosion at contacts caused by moisture, or a damaged coil spring in the steering wheel can also negatively impact the control unit’s self-test and trigger the error. Similarly, defective seatbelt locks or sensors within the airbag system may lead to this error code.

If all external components are intact, the root cause resides in the control unit. Defective electronic parts on the circuit board, damaged memory modules, faults in the internal diagnostic circuitry, or surge damage resulting from improper jump-starting are typical internal defects that give rise to B1505.

In which vehicles does error B1505 occur?

Error code B1505 is manufacturer‑independent but occurs more frequently in certain models from Peugeot, Mitsubishi, Dodge, and Hyundai. Notably affected are the airbag control units of the Peugeot 208 I and the Mitsubishi ASX. For these and other models, repair represents a cost‑effective alternative to replacing the entire component.

At Airbag24, we successfully repair error code B1505 for the following models and series:

Peugeot: 208 I (model years 2012–2015 and facelift 2015–2019)

Mitsubishi: ASX GA (from model year 2010 onward)

Dodge: Ram DS/DJ/D2 (model years 2009–2018)

Hyundai: Azera IG

In particular, for the Peugeot 208 I, the message “control unit failure” combined with B1505 is a well‑known issue pointing to an internal defect.

How is error B1505 professionally repaired?

Repair of error B1505 involves systematic analysis and restoration. Upon submission, the control unit undergoes a visual inspection and a thorough electronic diagnosis at Airbag24. Depending on the underlying cause, defective components are replaced, cold solder joints are reworked, or crash data is erased. Final tests confirm full functionality.

The repair process at Airbag24 begins with a detailed analysis. First, a visual inspection checks for external damage, corrosion, or water ingress. Subsequently, the control unit is read using specialized equipment to capture all stored errors and any existing crash data.

Based on the diagnostic results, targeted repairs are carried out. Defective electronic components on the circuit board, such as memory chips or processors, are professionally replaced. If crash data has been stored following an accident, it can be reset via the OBD‑2 interface using specialized software—this is possible in 95 percent of cases.

After hardware repair and software reset, the control unit undergoes a comprehensive functional test on a simulation bench. This ensures that the internal self‑test runs correctly again and that communication functions flawlessly. We provide 2 years' statutory liability for defects on the completed repair.

Is Repair Worth It for Error Code B1505?

Repairing the airbag control unit for error code B1505 is almost always the most cost‑effective solution. Compared to an expensive new part from the manufacturer, timely, condition‑appropriate refurbishment often saves substantial costs. Additionally, there’s no need for time‑consuming re‑coding of the control unit in the vehicle.

The biggest advantage is the cost savings. A repair can reduce expenses by up to 90 percent compared to purchasing a new control unit, which typically costs in the high three‑digit or even four‑digit range.

A refurbished original control unit is “plug-and‑play.” Since the vehicle‑specific configuration is preserved, no costly online programming or coding at an authorized dealer is required after reinstallation. The vehicle is ready for use immediately.