Airbag control unit with part number 985100070R

What does the airbag control unit 985100070R do?

The control unit 985100070R evaluates the restraint system (SRS) of Smart. In a crash, it decides within milliseconds which airbags and seatbelt pretensioners are triggered, and for this it checks the signals from the crash sensors.

In operation, the unit monitors the system continuously. If it detects a fault, it shows this via the airbag warning light in the instrument cluster.

After an accident, the unit stores crash data and locks itself.

Why does the control unit 985100070R fail?

The most common cause on the 985100070R is crash data from an accident, even if no airbag has been triggered; a normal diagnostic tool does not erase it. Other causes include ageing electronics, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

The crash data is held in the control unit and cannot be removed with ordinary tools, so this is part of the repair.

The other causes are technical in nature: components become prone to faults over time, solder joints lose their strength, and moisture affects the contacts. High voltage spikes, for example from a weak battery or jump-starting, can also cause damage.

How can you tell that the 985100070R is defective?

A defect in the 985100070R shows up as an airbag warning light that stays on permanently or intermittently, as a fault message in the instrument cluster, as a diagnostic tool without a connection to the control unit, and as a fault memory that cannot be cleared. In an emergency, the airbags and seatbelt pretensioners may then fail to trigger.

A warning light of this kind reports that the system itself has noticed something. The fact that the car moves normally in everyday use does not change this.

Please have the cause clarified promptly, before you rely on the restraint system.

Which vehicles is the 985100070R fitted in?

The control unit 985100070R is fitted in these vehicles: Smart Fortwo C453 (2014-2024).

The following vehicles are on record for this part number:

• Smart Fortwo C453 (2014-2024)

Comparing the part number on the label with this page only confirms that the unit is the right one. Before that, please have the fault memory read out, because only this result 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 A453 901 89 00, A4539001702, A4539017400.

How does the repair of the 985100070R work?

On the 985100070R, you first have the fault memory read out and the log enclosed. Then disconnect the battery and only afterwards remove the control unit. Next, create a repair order online and send in the well-packed unit.

Airbag24 checks the unit on the test bench, replaces defective components where necessary, erases the crash data and carries out a functional test. Processing usually takes 3–4 working days. After that, you receive your own unit back.

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 985100070R get to Airbag24?

You send the control unit 985100070R as a parcel, or book a UPS collection for an extra charge. After the repair, UPS brings the unit back from Airbag24.

The printed repair order goes into the parcel, and the unit is packed shock-proof.