Airbag control unit with part number 28556-4BU0A

What does the airbag control unit 28556-4BU0A do?

The airbag control unit 28556-4BU0A is the central control unit of the restraint system (SRS) of Nissan. It evaluates the signals from the crash sensors, determines in milliseconds in a collision whether airbags and seatbelt pretensioners are triggered, and monitors the system continuously. After an accident it stores crash data and locks itself.

Monitoring runs in the background. If the unit detects an irregularity, it reports it via the airbag warning light in the instrument cluster.

The control unit works together with sensors, wiring and the display. A fault in any of these parts can therefore show up in the control unit, even if the unit itself is intact.

Why does the control unit 28556-4BU0A fail?

The most common cause in the 28556-4BU0A control unit is crash data stored after an accident, even if no airbag has deployed. A normal diagnostic tool cannot erase this data. Other causes include aged components, moisture and voltage spikes.

Crash data remains stored in the control unit until the unit is repaired. It follows that a fault indication after an accident can remain even without visible damage.

The other causes concern the electronics and their connections. Electronic components age, solder joints can go cold, and corrosion at plug connectors can trigger faults. Voltage spikes, for example from a weak battery or a jump start, place additional strain on the circuitry.

How can you tell that the 28556-4BU0A is defective?

The airbag warning light in the instrument cluster lights up on the 28556-4BU0A control unit permanently or intermittently, and a fault message appears in the instrument cluster. The diagnostic tool cannot connect to the control unit, and the fault memory cannot be cleared. Airbags and seatbelt pretensioners may then fail to trigger in an emergency.

The light indicates that the system has detected a fault. Only the evaluation of the fault memory shows which cause lies behind it.

Which vehicles is the 28556-4BU0A fitted in?

The control unit 28556-4BU0A is fitted in: Nissan X-Trail T32 (2014-2017) and T32 Facelift (2017-2022).

The following overview lists the vehicles assigned to this part number.

• Nissan X-Trail T32 (2014-2017)
• Nissan X-Trail T32 Facelift (2017-2022)

Comparing the part number on the label of the removed unit with this page only shows that you have the right unit. Whether the control unit is defective or a connector or cable is the cause is shown only by the earlier reading of the fault memory.

For the same vehicles, we also repair control units with the part numbers 28556-4CG0A, 28556-4CH0A, 28556-4CJ0A, 28556-4CM0A, 28556-4CS0A, 98820-4CG0A.

How does the repair of the 28556-4BU0A work?

First have the fault memory read out and enclose the log. Then disconnect the battery and only then remove the control unit 28556-4BU0A. Next create a repair order online and send in the well-packed unit.

At Airbag24 the team checks the unit on the test bench, replaces defective components, erases stored crash data and carries out a functional test. You then receive your own unit back. Processing at Airbag24 usually takes 3–4 working days.

The order of steps is fixed for safety reasons. Our repairs come with 2 years' statutory liability for defects. The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.

How does the control unit 28556-4BU0A get to Airbag24?

You send the control unit 28556-4BU0A as a parcel to Airbag24, or you book a UPS collection for an extra charge. Airbag24 then sends the repaired unit back by UPS.

Put the printed repair order into the parcel and pack the unit shock-proof so that it survives shipping undamaged.