Airbag control unit with part number SC2EM3658100A

What does the airbag control unit SC2EM3658100A do?

The airbag control unit SC2EM3658100A forms the central control of the restraint system (SRS) in BYD vehicles. It processes the messages from the crash sensors, decides in a crash within a fraction of a second whether airbags and seatbelt pretensioners are triggered, and displays faults via the airbag warning light.

Outside of a crash, the unit continuously checks whether sensors, output stages and wiring are working properly. In doing so, it stores every irregularity that a diagnostic tool can read out later.

After a crash, the control unit writes crash data and locks itself. Only a repair lifts this lock again.

Why does the control unit SC2EM3658100A fail?

The most common cause is crash data stored after an accident, even if no airbag was triggered. This data cannot be erased with a normal diagnostic tool. Other causes include aged electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes, for example from a weak battery or after jump-starting.

The entries are not visible from the outside, but they are stored in the unit. They cannot be removed with the usual diagnosis, which is exactly why clearing them is part of the repair.

Airbag24 removes the crash data as part of the repair. The remaining causes are examined on the test bench and, where necessary, rectified by repair.

How can you tell that the SC2EM3658100A is defective?

The most important sign is the airbag warning light in the instrument cluster, which stays on permanently or only at times. Fault messages may appear, the diagnostic tool gets no connection to the control unit, and the fault memory cannot be cleared.

Such signs mean that the system has detected a fault. Airbags and seatbelt pretensioners can then fail to deploy even though the car looks unchanged from the outside.

A lit warning light is therefore a reason for a prompt check and should not be put off.

Which vehicles is the SC2EM3658100A fitted in?

The control unit SC2EM3658100A is fitted in these vehicles: BYD Atto 3 1st generation (2022-2025) and 1st generation Facelift (from 2026).

The following list shows the vehicles that Airbag24 has assigned to this part number:

• BYD Atto 3 1st generation (2022-2025)
• BYD Atto 3 1st generation Facelift (from 2026)

It is worth a comparison: checking the part number on the label of the removed unit against this page only confirms that it is the right unit. The cause is clarified only by the fault memory, which you should have read out beforehand. Only then does it become clear whether the control unit is defective or whether a plug or cable is causing the problem.

How does the repair of the SC2EM3658100A work?

First have the fault memory read out and enclose the report with the unit. Then disconnect the battery and only afterwards remove the control unit. Online, you create the repair order, and the well-packed unit goes to Airbag24.

This order protects you during removal and is therefore binding. Airbag24 then usually processes the shipment within 3–4 working days, and this time covers only checking, repairing and testing.

Airbag24 checks the unit on the test bench, repairs defective components, erases the crash data and carries out a function test. Afterwards, your own unit comes back 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 SC2EM3658100A get to Airbag24?

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

The printed repair order belongs in the parcel, and the unit should be packed shock-proof.