Airbag control unit with part number P31334738

What does the airbag control unit P31334738 do?

The airbag control unit P31334738 brings together all triggering decisions in the restraint system (SRS) of Volvo. It checks the crash sensors, decides in an accident on airbags and seatbelt pretensioners, and keeps the system under observation.

Within milliseconds the triggering decision is made. If the control unit detects a fault, it displays it via the airbag warning light in the instrument cluster.

After an accident it writes crash data to the memory and locks itself. Only the repair lifts the lock.

Why does the control unit P31334738 fail?

The most common cause is an entry from an accident involving the P31334738: crash data that remains in memory even when no airbag has triggered. A normal diagnostic tool cannot erase it. Other causes are aged electronics, moisture and corrosion at plugs, cold solder joints and voltage spikes.

The triggers break down as follows:

• crash data from an earlier accident
• aged electronic components
• moisture and corrosion at plug connections
• cold solder joints
• voltage spikes, for example from a weak battery or a jump start

Airbag24 removes the crash data during the repair, while the other causes are addressed during the testing and repair of the unit.

How can you tell that the P31334738 is defective?

A defect in the P31334738 becomes recognisable through the airbag warning light in the instrument cluster, either at times or constantly. Added to this are fault messages, a diagnostic tool without a connection, and a fault memory that cannot be cleared.

The signs in detail:

• airbag warning light that burns constantly or intermittently
• fault message in the instrument cluster
• no connection between the diagnostic tool and the control unit
• fault memory that cannot be cleared

As long as these signs persist, airbags and seatbelt pretensioners may not be able to trigger in an emergency. Clarify the finding promptly.

Which vehicles is the P31334738 fitted in?

The following models are currently stored. The control unit P31334738 is fitted in these vehicles: Volvo S40 M (2004-2007) and M Facelift (2007-2012).

Below you will find the list of the stored vehicles:

• Volvo S40 M (2004-2007)
• Volvo S40 M Facelift (2007-2012)

A comparison of the part number on the label with this page ensures that the removed unit is the right one. Whether it is defective, or whether a plug or cable causes the fault, is shown by the fault memory. Have it read out beforehand.

For the same vehicles, we also repair control units with the part numbers 30773401, 31334738, P30724427, P30724652, P30773354, P30773401.

How does the repair of the P31334738 work?

The fault memory of the P31334738 is read out first, and you enclose the log. Then disconnect the battery, remove the control unit, create the repair order online and send in the well-packed unit.

After that the work at Airbag24 follows: the unit is examined on the test bench, defective parts are replaced, the crash data is erased and a functional test is carried out. Your own unit goes back to you.

Processing at Airbag24 usually takes 3–4 working days, covering only checking, repairing and testing.

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 P31334738 get to Airbag24?

You send the control unit P31334738 as a parcel, or you book a UPS collection for an extra charge. After the repair, the unit is returned to you by UPS.

Put the printed repair order into the parcel. Make sure the unit is packed shock-proof.