Airbag control unit with part number BELG-57K30B

What does the airbag control unit BELG-57K30B do?

The airbag control unit BELG-57K30B is responsible for the restraint system (SRS) in Mazda. It evaluates the crash sensors, determines in an accident whether airbags and seatbelt pretensioners are triggered, and monitors the system without interruption. It reports detected faults via the airbag warning light.

An airbag only protects if it opens in time, so the evaluation runs without pause. The measured values are compared with stored limit values, and the result decides the triggering.

After an accident the control unit stores crash data and locks itself.

Why does the control unit BELG-57K30B fail?

The most common cause is stored crash data from an accident, even if no airbag has deployed. This data cannot be deleted with a normal diagnostic tool. Ageing electronics, cold solder joints, moisture at plug connections and voltage spikes are also possible.

The crash data remains in the unit, even if no airbag has deployed. This storage is one explanation that the check will clarify first.

The other causes concern the electronics: components age, solder joints can go cold, moisture and corrosion attack the plug connections, and voltage spikes occur, for example with a weak battery or a jump start.

How can you tell that the BELG-57K30B is defective?

The airbag warning light in the instrument cluster lights up permanently or intermittently, and a fault message appears in the instrument cluster. In addition, the diagnostic tool cannot reach the control unit, and the fault memory cannot be cleared.

The airbag warning light is the first to report when something is wrong in the restraint system. Airbags and seatbelt pretensioners may then not deploy in an emergency. A prompt check is therefore sensible.

Which vehicles is the BELG-57K30B fitted in?

The assignment applies to Mazda. The control unit BELG-57K30B is fitted in these vehicles: Mazda CX-5 KE (2011-2015) and KE Facelift (2015-2017).

The following vehicles are assigned to this control unit:

• Mazda CX-5 KE (2011-2015)
• Mazda CX-5 KE Facelift (2015-2017)

Comparing the part number on the label of the removed unit with this page only tells you about the unit itself. Whether the control unit is defective is shown only by the fault memory, which you should have read out beforehand, as it also shows whether a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers KA1C-57-K30A, KA1C-57K30, KD45-57K30B, KEAD 57K30 C, KR2757K30A.

How does the repair of the BELG-57K30B work?

First have the fault memory read out and enclose the log. Then disconnect the battery, remove the control unit and create a repair order online. Processing at Airbag24 usually takes 3–4 working days and covers only checking, repairing and testing the unit.

Then send the unit in, well packed. Airbag24 checks it on the test bench, replaces components where necessary and deletes the stored crash data. A functional test follows.

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 BELG-57K30B get to Airbag24?

You send the control unit as a parcel or book UPS collection for an extra charge. After repair it comes back to you from Airbag24 by UPS.

Enclose the printed repair order with the parcel, and the packaging should absorb shocks.