Airbag control unit with part number 28556AP002

What is the function of Airbag Control Unit 28556AP002?

The airbag control unit with part number 28556AP002 is the central control unit (SRS ECU) of the occupant protection system in vehicles such as the Nissan Micra K11 and March K11. It is responsible for processing signals from crash sensors and, in the event of an accident, precisely and promptly deploying the airbags and seatbelt pretensioners.

Under normal operating conditions, the control unit performs a self-test upon ignition. This is indicated by the brief illumination of the SRS warning light on the dashboard, which should extinguish after about two to three seconds. If the light does not go out, a system‑related fault is present.

The unit continuously monitors all components of the restraint system, from the sensors and airbag ignition circuits to the power supply. Its installation location is often in the center console, for example beneath the handbrake lever or in the rear section of the console.

Why does control unit 28556AP002 fail?

The most common cause of failure for control unit 28556AP002 is the storage of crash data following an accident, which results in the unit being locked. Other defects arise from age‑related hardware failures, mechanical damage to wiring, or corrosion at connector contacts, especially under the seats.

After an airbag deployment, crash data is permanently stored in the control unit’s internal memory. This lockout is a safety feature and cannot be cleared using standard diagnostic tools. The unit reports an internal error and must be professionally reset to restore functionality.

Electrical and mechanical issues are also prevalent. These include faulty cables connected to the seatbelt pretensioners or corroded connectors beneath the front seats, leading to error messages. Internal components on the circuit board may also fail due to aging or vibration.

A typical error code directly indicating an internal defect of the control unit is B1111. This code signals that repair or replacement of the unit is unavoidable, as the system is no longer functional.

How can you recognize a defect in 28556AP002?

The clearest symptom of a defective airbag control unit 28556AP002 is a constantly illuminated or flashing SRS warning light on the instrument cluster. This light does not turn off after starting the vehicle. Reading the fault memory often reveals persistent error codes such as B1111 (control unit defective), which cannot be cleared.

The airbag warning light serves as the primary alert for the driver. Ignoring this signal poses a significant safety risk, as neither the airbags nor the seatbelt pretensioners will deploy in the event of a crash. The vehicle’s entire passive safety system is thereby disabled.

During diagnostics at a workshop, it is also frequently observed that the control unit either fails to communicate with the OBD2 diagnostic tool or communicates only erratically. Stored crash data or severe internal hardware defects block access and prevent clearing of error messages.

In which vehicles is control unit 28556AP002 installed?

The airbag control unit with part number 28556AP002 is specifically designed for models in Nissan’s K11 series. At Airbag24, we accept this control unit for repair across the entire production period of the Nissan Micra K11, as well as for the identical Nissan March K11.

At Airbag24, we repair part number 28556AP002 for the following precisely matched models:

Nissan Micra K11 (1992–1998)

Nissan Micra K11 First Facelift (1998–2000)

Nissan Micra K11 Second Facelift (2000–2003)

Nissan March K11

How does the repair of 28556AP002 proceed?

Repair at Airbag24 begins after removal and shipment of the control unit. First, a technical analysis is conducted to identify the exact cause of the fault. The core process involves professionally erasing stored crash data and repairing any hardware defects to restore the device to its factory condition.

Before removing the control unit, it is advisable to inspect external sources of potential faults, such as connector contacts under the seats, for secure seating and signs of corrosion. After removal, the unit is carefully packaged and sent to Airbag24.

At the workshop, technicians thoroughly examine the unit. Repairs focus on eliminating blockages caused by crash data or resolving internal electronic malfunctions. Since the original control unit is repaired, all vehicle‑specific data remains intact, so no re‑coding or reprogramming is required after installation.

Finally, each repaired control unit undergoes a functional test on a specialized test bench to ensure the proper operation of all system components. Every repair is covered by 2 years' statutory liability for defects.

What are the benefits of repairing the 28556AP002?

The key advantage of repair is substantial cost savings—often exceeding 70% compared to purchasing an expensive new part. Since the original unit is refurbished, there’s no need for time-consuming re‑coding or programming of the control unit in the vehicle, saving both time and additional expenses.

A new manufacturer‑supplied control unit can involve significant costs. Repair offers an economically and technically sound alternative that restores the full functionality of the safety system.

By refurbishing the vehicle’s original control unit, compatibility is guaranteed at 100%. After installation, the system is immediately ready for use (plug-and-play). Professional execution by specialists and the included 2 years’ statutory liability for defects provide added peace of mind.