Airbag control unit with part number 985107805R

What does the airbag control unit 985107805R do?

The airbag control unit 985107805R is the central control unit of the SRS restraint system in Smart. It processes the signals from the crash sensors, decides in a collision whether airbags and seatbelt pretensioners are triggered, and monitors the system continuously.

The unit shows faults via the airbag warning light in the instrument cluster. After an accident, it stores crash data and locks itself.

In everyday life you notice little of this, because the control unit works quietly in the background. As soon as a message appears, a closer look is therefore worthwhile.

Why does the control unit 985107805R fail?

It may be due to stored crash data, even if no airbag deployed in an accident. A normal diagnostic tool cannot erase this data; Airbag24 erases it during the repair.

If you only clear the fault memory, the warning may return quickly, because the cause sits inside the unit. Simply clearing the fault at the vehicle does not solve the problem.

Other causes of failure are ageing electronic components, cold solder joints, moisture and corrosion at the plug connections, and voltage spikes from a weak battery or a jump start.

How can you tell that the 985107805R is defective?

A defect can show up as the airbag warning light in the instrument cluster, which lights up permanently or intermittently. Fault messages in the instrument cluster, a diagnostic tool without connection to the control unit and a fault memory that cannot be cleared come on top of this.

If the light goes out after a while, the cause has not been removed, because the entry may remain in the memory. The warning light alone therefore says little about the actual condition.

In an emergency, airbags and seatbelt pretensioners may not be able to deploy. A check should therefore not be put off for long.

Which vehicles is the 985107805R fitted in?

The control unit 985107805R is fitted in these vehicles: Smart Fortwo C453 (2014-2024).

The list shows the vehicles to which this control unit is assigned.

• Smart Fortwo C453 (2014-2024)

Before you remove the unit, have the fault memory read out. That establishes whether the control unit is really defective or whether a plug or cable is. Then compare the part number on the label of the removed unit with the information on this page.

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 985107805R work?

Processing at Airbag24 usually takes 3–4 working days. Beforehand, you have the fault memory read out, attach the log, disconnect the battery and remove the unit.

Then create a repair order online and send in the unit, well packed. At Airbag24 the unit is checked on the test bench, defective components are repaired, the crash data is erased and a functional test is carried out. Afterwards, your own unit is 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 985107805R get to Airbag24?

Either you send the unit in as a parcel, or you book a UPS collection for an extra charge. After the repair, it is returned to you by UPS.

The printed repair order goes in the parcel. The control unit should be packed shock-proof.