Airbag control unit with part number 3C0 909 605 D

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

The airbag control unit 3C0 909 605 D is the control unit of the SRS restraint system in Volkswagen vehicles. In an accident, it processes the signals from the crash sensors and decides within milliseconds whether airbags and seatbelt pretensioners are triggered. During operation it monitors the system and displays faults via the airbag warning light.

To do so, it continuously checks lines, sensors and the power supply. Any faults it finds are stored in the fault memory so that they become visible during a diagnosis.

After an accident, the unit stores crash data and is then locked. The lock is only lifted by the repair.

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

The most common cause is crash data from an accident, even if no airbag has deployed. Ageing components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes also come into question as causes.

• ageing of the electronic components
• cold solder joints
• moisture and corrosion at plug connections
• voltage spikes, for example from a weak battery or jump-starting

Crash data cannot be cleared with a normal diagnostic tool. The points listed above, by contrast, concern the condition and connections of the electronics.

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

The airbag warning light in the instrument cluster lights up intermittently or continuously. In addition, a fault message appears in the instrument cluster, the diagnostic tool has no connection to the control unit, and the fault memory cannot be cleared.

Signs like these mean that airbags and seatbelt pretensioners may fail to deploy in an emergency. The light shows the finding clearly, so it must be taken seriously.

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

The 3C0 909 605 D was fitted in this Volkswagen model: Volkswagen Passat B6 3C (2005-2010).

These vehicles are listed below:

• Volkswagen Passat B6 3C (2005-2010)

Comparing the part number on the label of the removed unit with this page gives you certainty that you have the right unit. It does not yet clear up the cause. For that, have the fault memory read out before removal, because it shows whether the control unit is defective or whether a plug or cable is causing the fault.

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 D work?

First, have the fault memory read out and enclose the log. Then disconnect the battery and remove the control unit. Processing at Airbag24 usually takes 3–4 working days for checking, repairing and testing.

Then create the repair order online and send the well-packed unit in. Airbag24 checks it on the test bench, replaces defective components, deletes the crash data and carries out a function test. The unit then goes back 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 D get to Airbag24?

You send the unit in as a parcel or book a UPS collection for an extra charge. Return shipping after the repair is made by UPS.

Pack the printed repair order into the parcel and protect the unit against shocks.