Airbag control unit with part number 985100655R

What does the airbag control unit 985100655R do?

The airbag control unit 985100655R controls the restraint system (SRS) of Smart. It evaluates the crash sensors and, in an accident, decides within milliseconds which airbags and seatbelt pretensioners are triggered.

The unit monitors the system constantly. If a fault is detected, it shows it via the airbag warning light in the instrument cluster.

If an accident has occurred, crash data is stored in the unit, and the unit is locked afterwards.

Why does the control unit 985100655R fail?

Crash data stored after an accident is among the most common causes, even if no airbag has deployed. This data cannot be erased with a normal diagnostic tool; at Airbag24 it is removed during the repair.

Aged electronic components can also cause the failure. Cold solder joints, moisture and corrosion on plug connections belong to the causes as well.

Finally, voltage spikes come into consideration, for example from a weak battery or a jump start. Such causes may only be clarified by testing.

How can you tell that the 985100655R is defective?

A defect on the 985100655R can be recognised by the airbag warning light, which stays on permanently or intermittently. In addition, fault messages may appear in the instrument cluster, the diagnostic tool finds no connection to the control unit, and the fault memory cannot be cleared.

If you notice such symptoms, you must reckon with airbags and seatbelt pretensioners possibly not deploying in an emergency. A check provides clarity here.

Which vehicles is the 985100655R fitted in?

This information applies to Smart. The 985100655R is fitted in these vehicles: Smart Fortwo C453 (2014-2024).

The vehicle list follows below:

• Smart Fortwo C453 (2014-2024)

Have the fault memory read before removal, so that it is clear whether the control unit itself is defective or whether a plug or a cable is the cause. Then compare the part number on the label of the removed unit with this information.

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 985100655R work?

First have the fault memory read and attach the log. Then disconnect the battery, remove the control unit, create a repair order online and send it in well packed.

Airbag24 checks the unit on the test bench, replaces defective components, deletes stored crash data and carries out a function test. The unit then goes back to you. Processing at Airbag24 usually takes 3–4 working days, counted only for checking, repairing and testing. 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 985100655R get to Airbag24?

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

Put the printed repair order in the parcel, and pack the control unit securely against shocks.