Airbag control unit with part number 3C0 909 605 A

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

The airbag control unit 3C0 909 605 A forms the central control unit of the restraint system (SRS) in Volkswagen. It continuously checks the crash sensors and, in an accident, decides in the shortest possible time which airbags and seatbelt pretensioners are triggered.

If a fault can be detected, the unit stores it and lets the airbag warning light in the instrument cluster come on.

After an accident it creates crash data and locks itself. More on this is in the next sections.

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

The most common cause for the 3C0 909 605 A is crash data that remains stored in the control unit after an accident, even if no airbag has triggered. Ordinary diagnostic tools cannot erase them. Other causes include ageing components, cold solder joints, moisture and corrosion, and voltage spikes.

Crash data remain stored after an accident, even when no airbag has deployed. As long as they are present, the fault cannot be fixed by an ordinary reading.

The other causes lie in the electronics. Components age, solder joints can go cold, and moisture or corrosion at plug connections disturb the signals. Voltage spikes, for example from a weak battery, also have an adverse effect.

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

The airbag warning light in the instrument cluster lights up permanently or intermittently if the 3C0 909 605 A has a defect. Fault messages in the instrument cluster, a missing connection to the diagnostic tool and a fault memory that cannot be cleared are added to this. In an emergency, airbags and seatbelt pretensioners may then fail to trigger.

The light shows the defect and cannot be overlooked. Anyone who notices it should have the system checked promptly.

The fault memory then clarifies which area is affected.

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

The control unit 3C0 909 605 A is fitted in these vehicles: Volkswagen Passat B6 3C (2005-2010).

The following list names the vehicles stored for this part number.

• Volkswagen Passat B6 3C (2005-2010)

Compare the part number on the label of the removed unit with this page. This comparison tells you nothing more than that you have the right unit in front of you. Have the fault memory read out beforehand: 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 3C0 909 605 F, 3C0 909 605J, 3C0 909 605M, 3C0909065F, 3C0909605K, 3C0909605N.

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

First have the fault memory read out and enclose the log. Then disconnect the battery and only then remove the control unit 3C0 909 605 A. Online, create a repair order and send the unit in well packed; at Airbag24, processing usually takes 3–4 working days.

Airbag24 checks the unit on the test bench, replaces defective components, erases crash data and carries out a function test. This time applies only to checking, repairing and testing at Airbag24.

Afterwards your own unit returns 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 3C0 909 605 A get to Airbag24?

The control unit 3C0 909 605 A goes to Airbag24 as a parcel, or you arrange a UPS collection for an extra charge. After the repair, it is sent back to you by UPS.

Enclose the printed repair order and use shock-resistant packaging.