Airbag control unit with part number A4518201585

What does the airbag control unit A4518201585 do?

The airbag control unit A4518201585 is the control unit of the restraint system (SRS) in Smart. It evaluates the crash sensors, triggers airbags and seatbelt pretensioners in an accident, and shows faults via the airbag warning light.

The system is checked continuously. After an accident, the unit stores crash data and locks itself.

It performs this task without the driver noticing anything, as long as the system works without faults.

Why does the control unit A4518201585 fail?

With the A4518201585, stored crash data is the most common cause of a fault, even if no airbag has deployed. A normal diagnostic tool cannot delete the data. Other causes include aged electronics, cold solder joints, moisture and corrosion, and voltage spikes.

With crash data in memory, the fault persists. Airbag24 removes the crash data during the repair.

Aged components and cold solder joints deteriorate over time. Moisture and corrosion at plug connections also act gradually.

Voltage spikes, for example from a weak battery or jump-starting, can damage individual components.

How can you tell that the A4518201585 is defective?

A defect on the A4518201585 can be recognised by several signs. In an emergency, airbags and seatbelt pretensioners may then fail to deploy.

The signs include:

• The airbag warning light stays on permanently or lights up intermittently.
• A fault message appears in the instrument cluster.
• The diagnostic tool has no connection to the control unit.
• The fault memory cannot be cleared.

The warning light is the message the system itself gives. A signal from the light calls for a check.

Which vehicles is the A4518201585 fitted in?

The airbag control unit A4518201585 is fitted in these vehicles: Smart Fortwo C451 (2007-2015).

The vehicles from the assignment can be found here:

• Smart Fortwo C451 (2007-2015)

Comparing the part number on the label with this page only ensures that you have removed the right unit. Have the fault memory read out beforehand, because only this result shows whether the control unit itself is defective or whether a connector 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 A4518201585 work?

With the A4518201585, the fault memory is read out first and the log is enclosed with the order; then you disconnect the battery, remove the control unit and create the repair order online. Processing at Airbag24 usually takes 3–4 working days.

Airbag24 checks the unit on the test bench, replaces defective components, deletes the crash data and carries out a functional test. Afterwards, your own 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 A4518201585 get to Airbag24?

The control unit A4518201585 is sent as a parcel or collected by UPS for an extra charge; after the repair it is returned to you by UPS.

Put the printed repair order into the parcel, and pack the unit shockproof.