Airbag control unit with part number 4M0959655BJ

What does the airbag control unit 4M0959655BJ do?

The control unit 4M0959655BJ coordinates the restraint system (SRS) of Audi. It evaluates the sensor signals in an impact and determines which airbags and seatbelt pretensioners fire. After an accident it stores crash data and locks itself.

Between events the monitoring runs without interruption. Every fault detected is logged in the fault memory, and the airbag warning light in the instrument cluster alerts the driver.

The unit links sensors, firing output stages and warning display. If it fails, this control over the entire system is lost.

Why does the control unit 4M0959655BJ fail?

The most common cause is crash data from an earlier accident, even if no airbag deployed in it. Other causes include aged components, cold solder joints, moisture and corrosion at connectors, and voltage spikes. With 4M0959655BJ, deleting the crash data is often not possible. If you want the crash data deleted, contact Airbag24 briefly before sending the unit in.

Crash data record what the unit registered during an event. They stay in memory even when the damage to the vehicle has long since been repaired.

The other causes build up over time. Electronic components age, solder joints can lose contact with temperature changes, and moisture disrupts signal transmission at connectors. Voltage spikes arise, for example, from a weak battery or when a jump-start is connected.

How can you tell that the 4M0959655BJ is defective?

A defect shows up as an airbag warning light that lights up permanently or intermittently, as a fault message in the instrument cluster, as a diagnostic tool with no connection to the control unit 4M0959655BJ, or as a fault memory that cannot be cleared. In such a case airbags and seatbelt pretensioners may not deploy in an emergency.

The overview of the individual signs:

• airbag warning light in the instrument cluster, permanently or intermittently
• fault message in the instrument cluster
• diagnostic tool receives no connection to the control unit
• fault memory cannot be cleared

The warning light is the clearest indication, because it shows the defect as soon as the control unit detects it. Even one of these signs alone is a clear reason to have the system checked promptly.

Which vehicles is the 4M0959655BJ fitted in?

The control unit 4M0959655BJ is fitted in these vehicles: Audi Q7 4M (2015-2019) and 4M Facelift (2019-2024); Audi SQ7 4M (2016-2019) and 4M Facelift (from 2019). The details relate to Audi.

The list below names the vehicles that are known to us for this part number.

• Audi Q7 4M (2015-2019)
• Audi Q7 4M Facelift (2019-2024)
• Audi SQ7 4M (2016-2019)
• Audi SQ7 4M Facelift (from 2019)

Compare the part number on the label of the removed unit with this page. That only ensures it is the right unit. Before removal, also have the fault memory read out, because only the log shows whether the control unit is defective or a connector or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 4KE959655B, 4KE959655J, 4KE959655L, 4M0 959 655 AF, 4M0 959 655 G, 4M0 959 655 K.

How does the repair of the 4M0959655BJ work?

Processing at Airbag24 usually takes 3–4 working days. First have the fault memory read out and attach the log, then disconnect the battery and only then remove the control unit 4M0959655BJ. Next, create a repair order online and send in the well-packed unit.

Airbag24 examines the unit on the test bench, repairs defective components and carries out a functional test. If you want the crash data erased, get in touch with Airbag24 briefly before sending it in. Your own unit is then sent back.

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 4M0959655BJ get to Airbag24?

You send the control unit 4M0959655BJ as a parcel, or book a UPS collection for an extra charge. After the repair, UPS takes the unit from Airbag24 back to you.

Place the printed repair order in the package, and pack the unit shock-proof.