Airbag control unit with part number A1698201085

What does the airbag control unit A1698201085 do?

The airbag control unit A1698201085 is the central control unit of the restraint system (SRS) for Mercedes-Benz. It analyses the signals from the crash sensors, decides in a crash within milliseconds on airbags and seatbelt pretensioners, and reports faults via the airbag warning light. After a crash it stores crash data and locks itself.

During driving the unit continuously checks whether the sensors, wiring and output stages are in order. It therefore constantly assesses the condition of the entire system.

In an emergency only a fraction of a second remains for the decision, so every triggering follows a fixed logic matched to the type of impact.

Why does the control unit A1698201085 fail?

The most common cause is crash data that the control unit A1698201085 stored after a crash, even if no airbag was deployed; a normal diagnostic tool cannot erase it. Other causes are ageing electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes, for example from a weak battery or a jump start.

Crash data is the record that the control unit creates in a crash. It is created even without an airbag being triggered.

The remaining causes concern the electronics themselves: components age, solder joints can go cold, and moisture or corrosion disturb signal transmission.

How can you tell that the A1698201085 is defective?

A defect shows as the airbag warning light in the instrument cluster lighting up permanently or intermittently, as an error message in the instrument cluster, as no connection between the diagnostic tool and 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.

The warning light is the clearest hint. If it does not go out after the ignition is switched on, or if it lights up again while driving, you should have this checked.

Which vehicles is the A1698201085 fitted in?

The airbag control unit A1698201085 is fitted in these vehicles: Mercedes-Benz B-Class W245 (2005-2011); Mercedes-Benz A-Class W169 (2004-2012).

Here are the vehicles for which this unit is listed:

• Mercedes-Benz B-Class W245 (2005-2011)
• Mercedes-Benz A-Class W169 (2004-2012)

First compare the part number on the label of the removed unit with this page; that only confirms that it is the right unit. Then have the fault memory read out, as only that 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 A1698201326, A1698202726, A1698204085, A1698206626, A1698206726, A1698207726.

How does the repair of the A1698201085 work?

First read out the fault memory and attach the log, then disconnect the battery and remove the control unit A1698201085. Next, create a repair order online and send in the well-packed unit. Inspection, repair and function test at Airbag24 usually take 3–4 working days.

At Airbag24 the unit is examined on the test bench, defective components are repaired and stored crash data is erased. The function test follows, and the repaired unit, which is your own, is returned to you.

The order is a matter of safety: the battery is only disconnected once the fault memory has been read out.

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 A1698201085 get to Airbag24?

You send the control unit A1698201085 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.