Airbag control unit with part number A4519017800

What does the airbag control unit A4519017800 do?

The airbag control unit A4519017800 forms the evaluation point for the crash sensors in the restraint system (SRS) for Smart. In an impact, it decides within milliseconds which airbags and seatbelt pretensioners trigger. During operation, it checks the system continuously and reports faults to the airbag warning light.

The check covers sensors, wiring and trigger circuits. If the control unit detects an irregularity, it writes it to the fault memory, from which the origin of the problem can be read later.

An accident leaves traces in the unit: it stores crash data and locks itself, regardless of whether an airbag has actually deployed.

Why does the control unit A4519017800 fail?

The most common cause is crash data stored after an accident, even if no airbag has deployed. A normal diagnostic tool cannot erase it. Other possible causes are ageing electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

The crash data is the first thing to check during fault-finding, because it remains in the unit even though the vehicle looks outwardly sound. A diagnostic tool cannot reach it in order to remove it.

The ageing of the electronics is a gradual process. Solder joints can give way with changing temperatures, and moisture or corrosion impair the contact at plug connections.

Voltage spikes, for example from a weakened battery or a jump start, put an additional strain on the electronics.

How can you tell that the A4519017800 is defective?

The airbag warning light lights up permanently or intermittently, a fault message appears in the instrument cluster, the diagnostic tool receives no connection to the control unit, and the fault memory cannot be cleared. In that case, airbags and seatbelt pretensioners may possibly not trigger in an emergency.

These signs help with classification:

• The airbag warning light in the instrument cluster lights up permanently or only intermittently.
• A fault message is shown in the instrument cluster.
• The diagnostic tool does not find the control unit.
• The fault memory cannot be emptied with the diagnostic tool.

The light indicates the fault as soon as the system detects it. Whether the control unit itself or a supply line is affected is clarified only by the evaluation.

Which vehicles is the A4519017800 fitted in?

The A4519017800 is fitted in these vehicles: Smart Fortwo C451 (2007-2015).

The list below shows the vehicles that Airbag24 has assigned to this part number.

• Smart Fortwo C451 (2007-2015)

Compare the part number on the label of the unit with this page. This comparison only confirms that you have the correct unit. Have the fault memory read out, because its log alone 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 A4519017800 work?

You 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 checks the unit on the test bench and replaces defective components. The team then erases the stored crash data and carries out a function test. Afterwards your own unit goes back to you.

The order of the steps is for your safety. The 3–4 working days relate solely to checking, repairing and testing at Airbag24.

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 A4519017800 get to Airbag24?

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

Put the printed repair order into the parcel and pack the unit shock-proof.