Airbag control unit with part number KD35-57K30C

What does the airbag control unit KD35-57K30C do?

The airbag control unit KD35-57K30C is the central control unit of the restraint system (SRS) for Mazda. It evaluates the signals from the crash sensors and, in an emergency, decides within milliseconds whether airbags and seatbelt pretensioners are triggered.

The unit monitors the system continuously and shows faults via the airbag warning light in the instrument cluster.

After an accident it stores crash data and locks itself. Only a repair lifts the lock.

Why does the control unit KD35-57K30C fail?

Crash data stored after an accident is the most common cause, even if no airbag has deployed. A normal diagnostic tool cannot erase it. Other causes are aged electronic components, cold solder joints, moisture and corrosion on plug connectors, and voltage spikes.

The crash data stays in the unit until Airbag24 erases it during the repair. Reading or erasing it with ordinary tools does not work.

The other causes relate to ageing and environmental influences inside the control unit. Aged components and cold solder joints alter its function, while moisture and corrosion attack the connectors.

How can you tell that the KD35-57K30C is defective?

A defect in the control unit KD35-57K30C shows itself through the airbag warning light, through fault messages, through a diagnostic tool without connection, or through a fault memory that cannot be cleared.

The following signs indicate a defect:

• Airbag warning light lit constantly or intermittently
• Fault message in the instrument cluster
• Diagnostic tool cannot find the control unit
• Fault memory cannot be cleared

In that case airbags and seatbelt pretensioners may not deploy in an emergency.

Which vehicles is the KD35-57K30C fitted in?

The airbag control unit KD35-57K30C is fitted in these vehicles: Mazda CX-5 KE (2011-2015) and KE Facelift (2015-2017).

The vehicles in which the unit is used are listed here:

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

Compare the part number on the label of the removed unit with this page; this only ensures that it is the correct unit. Have the fault memory read out beforehand. Only the log shows whether the control unit is defective or 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 KD35-57K30C work?

Processing at Airbag24 usually takes 3–4 working days. Airbag24 checks the control unit KD35-57K30C, repairs defective components, erases the crash data and carries out a function test.

First have the fault memory read out and attach the log. Then disconnect the battery. Only after that do you remove the unit.

Next, create a repair order online and pack the unit well before sending it in.

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 KD35-57K30C get to Airbag24?

You send the control unit KD35-57K30C as a parcel or book a UPS collection for an extra charge. After the repair Airbag24 returns it by UPS.

The printed repair order belongs in the parcel. Pack the unit shock-proof.