Airbag control unit with part number 4KE959655B

What is the function of the airbag control unit 4KE959655B?

The airbag control unit with part number 4KE959655B is the central control module for all restraint systems in the Audi SQ7 of the 4M series (model years 2016–2019, as well as the facelift from 2019 onward). It continuously monitors the vehicle’s sensors, processes their data, and determines, in the event of a crash, which airbags and seatbelt pretensioners need to be deployed.

As the “brain” of the passive safety system, this control unit processes signals from acceleration and pressure sensors distributed throughout the vehicle. Based on this information, it identifies the type and severity of a collision and activates the appropriate protective measures within milliseconds.

The control does not stop at front airbags alone. The unit coordinates the entire network of side airbags, head airbags, and seatbelt pretensioners to ensure optimal protection for all occupants.

Why does the control unit 4KE959655B fail?

Defects in the 4KE959655B control unit typically arise from three main causes: stored crash data following an accident that locks the system, moisture ingress damaging the electronics, or internal component failures. These hardware issues prevent proper operation and require specialized electronic repair.

One of the most common causes is the storage of crash data. After a collision, the control unit self‑locks for safety reasons. This condition is permanent and can only be reset through professional repair, which involves erasing the data on the memory chip.

Moisture can also cause severe damage to the electronics. Ingressing water leads to corrosion on the circuit board and may result in short circuits or failure of sensitive microchips.

Internal electronic faults—such as those affecting processors or memory modules—are another typical cause of failure. Similar and compatible part numbers like 4M0959655B, 4KE959655L, and 4M0959655, used in related models such as the Audi Q7 4M and Q8 4M, often exhibit identical fault patterns.

How do you recognize a defect in the 4KE959655B?

A defective 4KE959655B airbag control unit usually manifests as a permanently illuminated airbag warning light on the instrument cluster. Often, the control unit can no longer be read by a diagnostic tool because communication has been disrupted. Stored error codes that cannot be cleared are also clear indicators.

The primary symptom is the airbag warning light, which remains steadily illuminated or stays active for an unusually long time after engine start-up—typically around 30 seconds—signaling a malfunction in the restraint system.

Another critical sign is complete loss of communication. If a workshop attempts to read the control unit via the OBD interface, no response is received. The unit becomes inaccessible for diagnostic purposes.

Diagnostic logs frequently reveal error codes such as “Internal Control Unit Error” or specific errors related to side sensors that cannot be cleared. Even after replacing other components, such as the coil spring, the fault persists, indicating a defect within the control unit itself.

In which vehicles is the 4KE959655B control unit installed?

The 4KE959655B airbag control unit is primarily installed in Audi models. It is mainly found in the Audi SQ7 of the 4M series. Similar variants like 4M0959655B are also used in the Audi Q7 4M and Q8 4M. Airbag24 offers repair services specifically for these models.

At Airbag24, we repair the 4KE959655B control unit for the following models:

Audi SQ7 4M (model years 2016–2019)

Audi SQ7 4M Facelift (from model year 2019 onward)

Related part numbers such as 4M0959655B, 4KE959655L, and 4M0959655 are also installed in the Audi Q7 4M and Audi Q8 4M. Due to the very similar technical foundations, these models often experience the same types of defects.

It should be noted that replacement control units of this type typically require vehicle‑specific (VIN‑specific) pre‑programming. Therefore, repairing the original unit is often the simpler and more cost‑effective solution, as it avoids the need for complex re‑coding on the vehicle.

How is the 4KE959655B professionally repaired?

At Airbag24, repair of the 4KE959655B control unit begins with a precise initial inspection on specialized test benches. Subsequently, stored crash data is erased, defective electronic components are replaced, and the original software is restored. Following a thorough final check, you receive a fully functional component backed by 2 years’ statutory liability for defects.

The repair process at Airbag24 is designed to sustainably restore full functionality. It is recommended to have a diagnosis performed by a specialized workshop before removing the control unit and to include the shipment’s error log to expedite fault analysis.

Upon receipt of the unit, our specialized technicians conduct a thorough examination, checking the circuit board for moisture damage, internal short circuits, or signs of previous improper repair attempts.

The refurbishment includes professionally erasing crash data directly from the memory chip, replacing defective electronic components, and reprogramming the unit. Each repair is backed by 2 years’ statutory liability for defects on the work performed.