Airbag control unit with part number BCM5-57K30

What does the airbag control unit BCM5-57K30 do?

The BCM5-57K30 evaluates the signals from the crash sensors as the evaluation unit of the restraint system (SRS) of Mazda. In an accident, it decides within milliseconds which airbags and seatbelt pretensioners are triggered, and it monitors the system constantly. After an accident, it stores crash data and locks itself.

The airbag warning light is the visible interface to the driver. It lights up as soon as the system detects a fault.

The system works only through the interplay of sensors, triggers and the control unit.

Why does the control unit BCM5-57K30 fail?

The most common cause in the BCM5-57K30 is crash data stored after an accident, even if no airbag was deployed, and an ordinary diagnostic tool cannot remove it. Other causes are aged components, cold solder joints, moisture and corrosion on plug connectors, and voltage spikes, for example from a weak battery or a jump start.

The entry is not erased by continued use of the vehicle.

Over the years, solder joints can become brittle, and moisture attacks the contacts.

How can you tell that the BCM5-57K30 is defective?

A defect in the BCM5-57K30 shows up in the airbag warning light in the instrument cluster, when it lights up permanently or intermittently. A fault message in the instrument cluster, a missing connection to the diagnostic tool or a fault memory that cannot be cleared also point to a fault. With a defect, airbags and seatbelt pretensioners may possibly fail to trigger in an emergency.

The warning light is a direct signal from the system, which reports itself as soon as the system detects a fault.

Any one of these signs justifies a check, even if the vehicle otherwise runs normally. This applies especially if the light stays on permanently.

Which vehicles is the BCM5-57K30 fitted in?

The control unit BCM5-57K30 is found in the following vehicles: Mazda Mazda3 BL (2009-2011) and BL Facelift (2011-2013). The part number counts for the allocation, not the name of the car.

The list of vehicles recorded for this number follows below.

• Mazda Mazda3 BL (2009-2011)
• Mazda Mazda3 BL Facelift (2011-2013)

Compare the part number on the label of the removed unit with this page to make sure it is the right unit. Have the fault memory read out beforehand, because only that 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 0 285 001 960, B39G-57K30, BCF1-57K30, BFB6-57-K30, BFD1-57K30.

How does the repair of the BCM5-57K30 work?

Processing at Airbag24 for inspection, repair and testing takes 3–4 working days as a rule. Beforehand, have the fault memory read out, disconnect the battery and remove the control unit BCM5-57K30. Then create a repair order online and send in the unit well packed.

The order of the steps is binding, because the control unit is only removed after the battery has been disconnected. Airbag24 examines the unit on the test bench, repairs defective components, erases stored crash data and carries out a functional test.

Finally, your own unit returns to you. 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 BCM5-57K30 get to Airbag24?

You send the BCM5-57K30 by parcel, or you book a UPS collection for an extra charge. Airbag24 sends it back by UPS once the repair is complete.

The printed repair order belongs in the package. Pack the control unit so that it can be transported without damage from shocks.