Airbag control unit with part number A4519012801

What does the airbag control unit A4519012801 do?

In vehicles from Smart, the airbag control unit A4519012801 carries out the evaluation of the restraint system (SRS). Using the crash sensors, it assesses an impact and decides within milliseconds whether airbags and seatbelt pretensioners are triggered. To do so, it monitors the system constantly.

Detected faults are shown by the airbag warning light. After an accident, the unit stores crash data and locks itself; only the repair lifts this lock.

Why does the control unit A4519012801 fail?

The most common cause is stored crash data after an accident, even if no airbag has deployed; a normal diagnostic tool does not remove it. Aged electronic components, cold solder joints, moisture and corrosion on plug connectors, and voltage spikes are also possible causes.

The crash data stays in the unit until the repair removes it. A diagnosis without reading out the fault memory gives no certainty here.

Electronics and the power supply make up the other causes. Which of them applies is shown only by the fault memory log.

How can you tell that the A4519012801 is defective?

The airbag warning light in the instrument cluster lights up permanently or intermittently. Accompanying signs can be an error message in the instrument cluster, a diagnostic tool without connection to the control unit, and a fault memory that cannot be cleared.

As long as such a fault exists, airbags and seatbelt pretensioners may possibly not trigger in an emergency. For this reason, a prompt check is advisable.

Whether the control unit itself is affected is shown only by reading out the fault memory.

Which vehicles is the A4519012801 fitted in?

The control unit A4519012801 is fitted in these vehicles: Smart Fortwo C451 (2007-2015). This assignment rests solely on the part number.

These vehicles are on record for this part number:

• Smart Fortwo C451 (2007-2015)

Compare the part number on the label of the removed unit with this page; this establishes whether it is the right unit. The comparison does not answer the question of the cause, however. Have the fault memory read out beforehand, because only then will it become clear whether the control unit is defective or whether a plug or a cable is the trigger.

For the same vehicles, we also repair control units with the part numbers A451 820 24 85, A4518201585/001, A4518202285, A4518202485/002, A4519011300Q02.

How does the repair of the A4519012801 work?

First, have the fault memory read out and attach the log. Then disconnect the battery and only afterwards remove the control unit. Last, create the repair order online and pack the unit well for sending.

Airbag24 examines the unit on the test bench, replaces damaged components and removes the stored crash data. A function test follows. Processing at Airbag24 usually takes 3–4 working days, after which your unit is 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 A4519012801 get to Airbag24?

You send the unit in as a parcel; alternatively, UPS collects it from your address for an extra charge. After the repair, UPS brings it back to you.

The printed repair order goes into the parcel, and the unit is packed so that it withstands shocks.