Airbag control unit with part number A2049013402

What does the airbag control unit A2049013402 do?

The A2049013402 controls the restraint system of Mercedes-Benz as the airbag control unit. In an impact it checks the measurements from the crash sensors and triggers the appropriate airbags and seatbelt pretensioners within milliseconds.

During operation the system checks itself. If this self-test detects a fault, the unit reports it via the airbag warning light in the instrument cluster, so you can keep an eye on the condition at all times.

After an accident the unit stores crash data and locks itself. This point also concerns how the removed unit is handled.

Why does the control unit A2049013402 fail?

The most common cause for the A2049013402 is crash data stored after an accident, even if no airbag has deployed. Further causes include aged components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

Crash data cannot be erased with a normal diagnostic tool. The unit therefore keeps it in memory, and Airbag24 erases it during repair.

Other causes at a glance:

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

How can you tell that the A2049013402 is defective?

The airbag warning light in the instrument cluster stays on permanently or intermittently. On the A2049013402, a fault is also indicated by an error message in the instrument cluster, by the diagnostic tool finding no connection to the control unit, or by a fault memory that cannot be cleared.

The warning light is the most visible sign of a fault in the restraint system. It shows that the system is not fully functional, which is exactly why it is worth looking at the instrument cluster.

In an emergency, airbags and seatbelt pretensioners may then fail to deploy. Such a warning therefore requires prompt clarification.

Which vehicles is the A2049013402 fitted in?

Whether your own car is affected can be checked with the vehicle papers. The A2049013402 is fitted in these vehicles: Mercedes-Benz C-Class S204 Estate (2007-2014), W204 Saloon (2007-2014) and C204 Coupé (2011-2015).

The following vehicles are assigned to the unit:

• Mercedes-Benz C-Class S204 Estate (2007-2014)
• Mercedes-Benz C-Class W204 Saloon (2007-2014)
• Mercedes-Benz C-Class C204 Coupé (2011-2015)

Compare the part number on the label of the removed unit with this page, so you can see it is the correct unit. Also have the fault memory read out beforehand, because this log shows whether the control unit is defective or a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 2048709426, 5WK44740, A204 870 68 26, A204 901 26 04, A204 901 35 02, A2048208285.

How does the repair of the A2049013402 work?

First have the fault memory read out and attach the log, then disconnect the battery and remove the A2049013402. Then create a repair order online and send the unit in well packed. Processing at Airbag24 usually takes 3–4 working days.

Airbag24 tests the unit on the test bench, finds and repairs defective components, erases the stored crash data and carries out a function test. Your own unit is then returned 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 A2049013402 get to Airbag24?

You send the A2049013402 as a parcel or book a UPS collection for an extra charge. After the repair, Airbag24 sends the unit back to you by UPS.

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