Airbag control unit with part number A4519012101

What does the airbag control unit A4519012101 do?

The airbag control unit A4519012101 is the central control unit of the restraint system (SRS) for Smart. It evaluates the signals from the crash sensors and decides in an emergency which airbags and seatbelt pretensioners are triggered.

The evaluation takes place in a fraction of a second. The unit checks the strength and direction of the impact and activates only the restraint devices that suit the situation.

During operation it checks all connected components. If it detects a fault, it stores it and reports it via the airbag warning light. After an accident it records crash data and locks itself.

Why does the control unit A4519012101 fail?

The most frequent cause is crash data stored after an accident, even if no airbag was triggered. A normal diagnostic tool cannot erase it. Ageing components, cold solder joints, moisture and corrosion, and voltage spikes are also possible causes.

Stored crash data comes first on this list. It is created by an impact in which no airbag triggers, and it stays in the unit until it is removed.

Ageing electronic components and cold solder joints lead to intermittent faults over time. Moisture and corrosion at plug connections impair the connection.

Voltage spikes, for example from a weak battery or jump-starting, put additional strain on the electronics.

How can you tell that the A4519012101 is defective?

A defect shows up as an airbag warning light that stays on permanently or intermittently, a fault message in the instrument cluster, no connection to the diagnostic tool, or a fault memory that cannot be cleared. In an emergency, airbags and seatbelt pretensioners may then fail to trigger.

• Airbag warning light on permanently or intermittently
• Fault message in the instrument cluster
• Diagnostic tool receives no connection to the control unit
• Fault memory cannot be cleared

The warning light is the most important of these signs. If it comes on, have the system checked promptly.

Which vehicles is the A4519012101 fitted in?

The A4519012101 is fitted in these vehicles: Smart Fortwo C451 (2007-2015).

The overview shows the vehicles for this part number.

• Smart Fortwo C451 (2007-2015)

Compare the part number on the label of the removed unit with this page. This only confirms that it is the correct unit.

Read out the fault memory first. Only the log shows whether the control unit is defective or whether a plug or cable is the cause.

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 A4519012101 work?

First have the fault memory read out and enclose the log. Then disconnect the battery and only then remove the control unit. Next, 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, replaces defective components and erases the stored crash data. A function test follows.

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 A4519012101 get to Airbag24?

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

The printed repair order goes in the parcel. Pack the control unit shockproof.