Airbag control unit with part number A2179000501

What does the airbag control unit A2179000501 do?

As the airbag control unit A2179000501 from Mercedes-Benz, the module forms the switching centre of the restraint system. It processes the messages from the crash sensors and decides within milliseconds whether airbags and seatbelt pretensioners are triggered.

In operation, the unit continuously checks all components of the system. If it detects a fault, it passes this on to the driver via the airbag warning light.

After an accident, the control unit stores crash data and then remains locked.

Why does the control unit A2179000501 fail?

The most common cause: crash data stored after an accident, even if no airbag has deployed. Added to this are aged electronic components, cold solder joints, moisture and corrosion at plug connectors, and voltage spikes such as those from a weak battery or a jump start.

A standard diagnostic tool cannot remove stored data of this kind. That is precisely why the fault persists until the control unit is repaired.

The other causes relate to the circuit itself: components wear over time, solder joints lose their hold, and moisture or rust on the plugs disturbs the contact.

How can you tell that the A2179000501 is defective?

On the A2179000501, a defect becomes noticeable through the airbag warning light, which lights up permanently or intermittently. A fault message may also appear in the instrument cluster, the diagnostic tool may not find the control unit, or the fault memory cannot be erased.

In that case there is a risk that airbags and seatbelt pretensioners will not deploy in an emergency. Please take the warning seriously and clarify the cause promptly.

Which vehicles is the A2179000501 fitted in?

First check whether your car is included. The control unit A2179000501 is fitted in these vehicles: Mercedes-Benz S-Class C217 Coupé (2014-2020) and A217 Convertible (2014-2020).

The vehicles known to us for this part number can be found here:

• Mercedes-Benz S-Class C217 Coupé (2014-2020)
• Mercedes-Benz S-Class A217 Convertible (2014-2020)

Comparing the part number on the label of the removed unit with this page only ensures that it is the correct unit. Have the fault memory read out beforehand, because only this shows whether the control unit itself is defective or a plug or cable is causing the fault.

For the same vehicles, we also repair control units with the part numbers A2179008302, A2229000303, A2229009908, A2229013503.

How does the repair of the A2179000501 work?

First have the fault memory read out and keep the log. Then disconnect the battery and remove the A2179000501. Next, create a repair order online and send in the well-packed unit; Airbag24 checks and repairs it, replaces defective components, erases stored crash data and tests the function.

Processing at Airbag24 usually takes 3–4 working days. This means the time for testing, repair and function test, not your steps and not the dispatch.

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 A2179000501 get to Airbag24?

You send the A2179000501 control unit to Airbag24 as a parcel, or you book a UPS collection for an extra charge. Airbag24 sends your own unit back to you by UPS after the repair.

The printed repair order goes into the parcel. Pack the unit so that it is shockproof.