Airbag control unit with part number 51904689

What does the airbag control unit 51904689 do?

The 51904689 is the central unit of the SRS for Fiat. It evaluates the crash sensors, decides in a collision within milliseconds whether airbags and seatbelt pretensioners are triggered, and monitors the system continuously.

The unit shows faults via the airbag warning light, so that they can be recognised in the instrument cluster.

After an accident it stores crash data and locks itself. The lock is released only by a repair.

Why does the control unit 51904689 fail?

The most common cause is stored crash data remaining after an accident, even without a triggered airbag. In addition, there are further causes in brief: ageing components, cold solder joints, moisture and corrosion on plug connectors, and voltage spikes.

Crash data cannot be deleted with a normal diagnostic tool. The problem therefore persists until the control unit has been repaired.

• ageing electronic components
• cold solder joints
• moisture and corrosion on plug connectors
• voltage spikes, for example from a weak battery or a jump start

This list gives general causes that may come into consideration in the event of a failure.

How can you tell that the 51904689 is defective?

The airbag warning light in the instrument cluster lights up permanently or intermittently, or an error message appears in the instrument cluster. In addition, the diagnostic tool cannot reach the control unit, and the fault memory cannot be cleared. In this case, airbags and seatbelt pretensioners may possibly fail to deploy in an emergency.

These signs indicate a defect, even if the vehicle appears to drive normally in everyday use.

If the warning light stays on permanently, have the system read out promptly.

Which vehicles is the 51904689 fitted in?

The list will tell you whether your vehicle is affected. The 51904689 is fitted in these vehicles: Fiat 500 312 (2007-2024).

The list shows the vehicles for which this part number is known:

• Fiat 500 312 (2007-2024)

Check the part number on the label of the removed unit against this page. This only tells you that it is the correct unit. Have the fault memory read out in advance. Only the 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 51782985, 51870005, 51897810, 51918659, 51963734, 519637734.

How does the repair of the 51904689 work?

First have the fault memory read out and attach the log. Then disconnect the battery and remove the control unit before you create the repair order online. Processing at Airbag24 usually takes 3–4 working days.

Airbag24 tests the unit on the test bench, replaces defective components, deletes the crash data and carries out a function test. The own 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 51904689 get to Airbag24?

You send the unit as a parcel or arrange a UPS collection for an extra charge. After the repair, Airbag24 sends it back to you by UPS.

Place the printed repair order in the parcel. Pack the control unit shock-proof.