Airbag control unit with part number 3C0 909 605 B

What does the airbag control unit 3C0 909 605 B do?

In the restraint system (SRS) of Volkswagen, the airbag control unit 3C0 909 605 B is the point that coordinates everything. It reads the signals from the crash sensors and, in a crash, decides within milliseconds which airbags and seatbelt pretensioners are triggered. Between events, it monitors the entire system.

Faults are shown via the airbag warning light in the instrument cluster. After a crash, it stores crash data and locks itself.

The safety of the occupants therefore depends on this unit working reliably.

Why does the control unit 3C0 909 605 B fail?

The most common cause is the crash data stored after an accident, even if no airbag was triggered; a normal diagnostic tool cannot erase it. Other causes are ageing electronic components, cold solder joints, moisture and corrosion on plug connections, and voltage spikes, for example from a weak battery or jump-starting.

Crash data is also recorded if the accident did not trigger the airbags. Only Airbag24 removes it, during the repair.

The remaining causes arise in the electronics or at the connections. Moisture and corrosion attack the contacts, cold solder joints can interrupt connections, and voltage spikes stress components that need a steady voltage.

How can you tell that the 3C0 909 605 B is defective?

The airbag warning light in the instrument cluster lights up permanently or only at times. Other signs are a fault message in the instrument cluster, a missing connection between the diagnostic tool and the control unit, and a fault memory that cannot be cleared.

If the warning light is on, the control unit is signalling a fault that it has detected itself. In that case, the airbags and seatbelt pretensioners may not be able to trigger in an emergency.

Please look into such signs promptly and have the fault memory read out.

Which vehicles is the 3C0 909 605 B fitted in?

This information refers to part number 3C0 909 605 B. The airbag control unit 3C0 909 605 B is fitted in these vehicles: Volkswagen Passat B6 3C (2005-2010).

The following vehicles belong to this part number:

• Volkswagen Passat B6 3C (2005-2010)

Comparing the part number on the removed unit with this page only confirms that it is the correct unit. Whether the control unit is faulty, or whether a plug or cable is the cause, is established by the fault memory. Please have it read out in advance.

For the same vehicles, we also repair control units with the part numbers 3C0 909 605 F, 3C0 909 605J, 3C0 909 605M, 3C0909065F, 3C0909605K, 3C0909605N.

How does the repair of the 3C0 909 605 B work?

Have the fault memory read out and keep the log so you can enclose it later. Disconnect the battery before removing the control unit. Then create a repair order online and send in the well-packed unit.

Airbag24 checks the unit on the test bench, replaces defective components and erases the stored crash data. This is followed by a function test, after which your own unit is returned to you.

For checking, repairing and testing, Airbag24 usually needs 3–4 working days. 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 3C0 909 605 B get to Airbag24?

Either you send the unit as a parcel, or you book a UPS collection for an extra charge. After the repair, it is returned by UPS. Put the printed repair order in the parcel and pack the unit shockproof.

When packing, make sure the housing is not exposed to knocks. That way the unit arrives undamaged.