B1557 airbag control unit fault

What does error code B1557 mean?

Error code B1557 indicates a critical, internal circuit fault in the airbag control unit (SRS ECU). This points to a permanent hardware defect on the circuit board that cannot be resolved by a simple software reset or disconnecting the battery. The control unit has detected an irreparable electronic failure within its own components.

Technically speaking, B1557 stands for “SRS ECU (Supplemental Restraint System) internal circuit fault.” The control unit’s self-diagnostic system continuously monitors its internal circuits. When an irregularity or defect is detected in an internal component that falls outside acceptable tolerances, this error code is permanently stored in the fault memory.

Unlike sporadic errors caused, for example, by voltage fluctuations or loose connections, B1557 signals a deep-seated, physical issue within the control electronics. A professional repair at the component level is therefore unavoidable.

How can you recognize error B1557?

The most obvious symptom of error B1557 is the permanently illuminated airbag or SRS warning light on the instrument panel. This warning indicates a failure of the restraint system, meaning the airbags may not deploy in the event of a crash. In some cases, communication with the control unit via a diagnostic tool is also no longer possible.

The airbag warning light does not turn off after starting the vehicle. This shows that during its self-test, the system identified a severe, persistent fault and has entered a safety mode.

If the control unit, due to the internal defect, no longer responds to requests from a diagnostic device, it becomes impossible to read additional error codes or system data. This confirms the severity of the internal hardware problem.

What causes B1557?

The direct cause of error code B1557 is an internal hardware defect in the airbag control unit. It involves a fault in the electronic circuits on the device’s circuit board. General issues in the airbag system, such as defective connectors or sensors, typically result in other error codes; B1557 isolates the problem to the control unit itself.

While B1557 specifically denotes an internal defect, external factors can contribute to such damage. These include water ingress through leaks in the vehicle, leading to corrosion and short circuits on the circuit board.

General mechanical stress or aging of electronic components can also lead to these internal faults. Defective cables, poor connector contacts, or a worn coil spring in the steering wheel are common sources of problems in the airbag system, but they usually trigger other, more specific error codes that point to those external components.

Which vehicles are affected by B1557?

Error code B1557 occurs frequently in certain vehicle models manufactured by Mitsubishi. The ASX series, in particular, is well-known for this specific internal control unit fault. At Airbag24, we professionally and reliably repair this error for a range of Mitsubishi models.

At Airbag24, we repair error code B1557 for the following models, among others:

Mitsubishi: ASX (GA series, from model year 2010 onward), Pajero Sport (QE series), Pajero iO (H60 series)

How is B1557 professionally repaired?

Repairing error B1557 requires specialized electronic repair at the component level. After removing and sending the control unit to Airbag24, a systematic analysis of the circuit board is performed to identify the faulty circuit. Experienced technicians then precisely fix the issue and thoroughly test the device.

The first step in the workshop is diagnosis. Before dismantling the control unit, the fault memory should be read out to confirm B1557 as the primary cause and rule out other potential sources of trouble in the system.

Following shipment to Airbag24 comes the technical analysis. Using advanced measurement technology, the control unit’s circuit board is examined to pinpoint the exact source of the fault. This process demands profound expertise in electronics.

Once the defect is located, the faulty component on the circuit board is expertly replaced, or the damaged circuit is repaired. Upon completion of the repair, the control unit undergoes comprehensive testing to ensure full functionality. A 12-month warranty is provided for all repairs performed.