Airbag control unit with part number A2049010604

What does the airbag control unit A2049010604 do?

The A2049010604 is the airbag control unit in the restraint system of Mercedes-Benz. It evaluates the signals from the crash sensors and decides in an accident within milliseconds which airbags and seatbelt pretensioners are triggered.

The unit checks the entire system without interruption. If it finds a fault, it reports it via the airbag warning light in the instrument cluster, so that the state stays visible at all times.

After an accident the unit stores crash data and locks itself. This process must be taken into account in every repair.

Why does the control unit A2049010604 fail?

The most common cause for the A2049010604 is crash data stored after an accident, even without a triggered airbag. Other causes are aged components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

Crash data cannot be erased with a normal diagnostic tool. Airbag24 removes it during repair.

Other causes include:

• aged electronic components
• cold solder joints
• moisture and corrosion at plug connections
• voltage spikes, for example from a weak battery

How can you tell that the A2049010604 is defective?

The airbag warning light in the instrument cluster stays on permanently or intermittently. A defect on the A2049010604 also shows as an error message, as a missing connection of the diagnostic tool, or as a fault memory that cannot be cleared.

The warning light is the first visible sign. It shows that the restraint system is not fully functional.

If the control unit is defective, airbags and seatbelt pretensioners may fail to deploy in an emergency. Such an indication therefore requires prompt clarification.

Which vehicles is the A2049010604 fitted in?

A comparison with the vehicle data shows whether your own car is affected. The A2049010604 is fitted in these vehicles: Mercedes-Benz C-Class S204 Estate (2007-2014), W204 Saloon (2007-2014) and C204 Coupé (2011-2015).

The vehicles are listed here:

• 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 first. This only confirms that it is the correct unit. Have the fault memory read out beforehand, because only the log shows whether the control unit itself 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 A2049010604 work?

First have the fault memory read out and attach the log. Then disconnect the battery and only then remove the A2049010604, and create a repair order online.

Send the well-packed unit in. Airbag24 examines it on the test bench, repairs defective components, erases the stored crash data and carries out a function test. Processing usually takes 3–4 working days. Your own unit is then returned.

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 A2049010604 get to Airbag24?

You send the A2049010604 as a parcel or book a UPS collection for an extra charge. After the repair, Airbag24 sends the unit back by UPS.

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