Airbag control unit with part number A2389002104

What does the airbag control unit A2389002104 do?

Within the restraint system (SRS) of Mercedes-Benz, the airbag control unit A2389002104 is the control centre. From the signals of the crash sensors it determines in an accident which airbags and seatbelt pretensioners fire. It checks the system continuously and reports faults via the warning light.

After an accident, the control unit records crash data and locks itself. You cannot see this while driving.

Why does the control unit A2389002104 fail?

Stored crash data is the most common cause, even when no airbag has deployed, and an ordinary diagnostic tool cannot erase it. In addition there are ageing components, dry solder joints, moisture and corrosion, and voltage spikes.

The crash data is created in the unit itself and does not affect the airbags. So it cannot be identified from the deployment alone.

The remaining causes develop over a longer period or occur through electrical stress. Solder joints go cold, electronics age, and moisture or corrosion damage the plug connectors.

How can you tell that the A2389002104 is defective?

A defect shows up mainly as the airbag warning light, which lights up permanently or intermittently. In that case, airbags and seatbelt pretensioners may not deploy in an emergency.

Typical signs are:

• airbag warning light in the instrument cluster
• fault message in the instrument cluster
• no connection between the diagnostic tool and the control unit
• fault memory that cannot be cleared

Take each of these signs seriously, even if the light only comes on intermittently.

Which vehicles is the A2389002104 fitted in?

The following vehicles are assigned to the unit A2389002104: Mercedes-Benz E-Class C238 Coupé (2016-2023) and A238 Convertible (2017-2023).

The assignment in detail:

• Mercedes-Benz E-Class C238 Coupé (2016-2023)
• Mercedes-Benz E-Class A238 Convertible (2017-2023)

Comparing the part number on the label with this page confirms that you have the right unit. Whether the control unit is defective, or whether a plug or cable causes the fault, only becomes clear when the fault memory is read out. So have it read out beforehand.

For the same vehicles, we also repair control units with the part numbers A2139003617, A2389008100.

How does the repair of the A2389002104 work?

You begin by having the fault memory read out and attach the log, then disconnect the battery. Only after that remove the control unit A2389002104 and create a repair order online. Airbag24 needs 3–4 working days for checking, repairing and testing.

Airbag24 checks the unit on the test bench, replaces defective components, erases the stored crash data and carries out a function test.

The order of steps is there to protect when working on the airbag system, and it must therefore be followed.

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 A2389002104 get to Airbag24?

You send the control unit A2389002104 to Airbag24 as a parcel, or you book a UPS collection for an extra charge. After the repair, it is returned by UPS.

Put the printed repair order into the parcel and pack the unit shock-resistant.