Airbag control unit with part number BS4H-57K30A

What does the airbag control unit BS4H-57K30A do?

The airbag control unit BS4H-57K30A acts as the central unit that controls the restraint system (SRS) of Mazda. It checks the signals from the crash sensors and, in an accident, decides within milliseconds which airbags and seatbelt pretensioners are triggered.

The housing also carries the manufacturer's part number Bosch 0285001961. Beyond that, the unit monitors the system continuously and reports faults via the airbag warning light.

After an accident it stores crash data and locks itself.

Why does the control unit BS4H-57K30A fail?

The most common cause on the BS4H-57K30A is crash data from an accident, even if no airbag has triggered. A standard diagnostic tool cannot remove it. Further causes are also possible.

In detail, these are mainly:

• aged electronic components
• cold solder joints
• moisture and corrosion at plug connections
• voltage spikes, for example from a weak battery or jump-starting

Stored crash data stays in the unit until it is deleted. An airbag does not have to have triggered for this.

How can you tell that the BS4H-57K30A is defective?

A defect on the BS4H-57K30A shows up as warning signals in the instrument cluster. In addition, the fault memory cannot be cleared, and the diagnostic tool does not find the control unit.

The signs at a glance:

• airbag warning light on permanently or intermittently
• fault message in the instrument cluster
• diagnostic tool receives no connection to the control unit
• fault memory cannot be cleared

With such a defect, airbags and seatbelt pretensioners may possibly not trigger in an emergency. The warning light is therefore a reason to have the system checked promptly.

Which vehicles is the BS4H-57K30A fitted in?

The control unit BS4H-57K30A is fitted in these vehicles: Mazda Mazda3 BK Facelift (2006-2009) and BK (2003-2006). The information applies to this part number and to no other.

Here follows the list of vehicles:

• Mazda Mazda3 BK Facelift (2006-2009)
• Mazda Mazda3 BK (2003-2006)

Comparing the part number on the label of the removed unit with this page ensures that you have the right unit. Also have the fault memory read out before removal. Only this result shows whether the control unit itself is defective or whether a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 131000-1022, 285001453, 285001553, 285001554, BP4K-57K30, BP4K-57K30B.

How does the repair of the BS4H-57K30A work?

First have the fault memory read out and enclose the log. Then disconnect the battery and only then remove the control unit BS4H-57K30A. Next, create a repair order online and send in the well-packed unit.

Airbag24 examines the unit on the test bench, repairs defective components, deletes stored crash data and carries out a function test. Afterwards your own unit goes back to you. Processing at Airbag24 generally takes 3–4 working days.

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 BS4H-57K30A get to Airbag24?

Either you send the control unit BS4H-57K30A yourself as a parcel, or you book a UPS collection for an extra charge. Airbag24 sends the unit back to you by UPS after the repair.

Put the printed repair order into the parcel and pack the unit shockproof.