Airbag control unit with part number 5Q0 959 655 AQ

What is the function of the airbag control unit 5Q0959655AQ?

The airbag control unit 5Q0959655AQ is the central control module of the occupant protection system (SRS) in vehicles based on the VW/Audi MQB platform. It continuously analyzes data from acceleration and crash sensors and, in the event of a collision, determines whether and which restraint systems—such as airbags and seatbelt pretensioners—should be deployed.

As an SRS control unit, this component is safety-critical. It communicates via the CAN bus with other vehicle control units to ensure precise operation and to report the system status to the instrument cluster.

The proper functioning of the control unit is crucial, as a failure could result in airbags or seatbelt pretensioners not activating during a real‑world accident.

What types of defects occur in the 5Q0959655AQ?

The most common causes of failure for the control unit 5Q0959655AQ are stored crash data following an accident that prevents further use, as well as internal hardware defects. These include memory errors (EEPROM/Flash), defective SMD components on the circuit board, or communication issues caused by faulty CAN transceivers.

After a crash, the control unit stores so‑called “crash data” or sets a “crash flag.” This is a safety feature that locks the device, requiring professional diagnostics and a reset before it can be reused.

Another frequent source of failure is internal electronic malfunctions. These may involve damaged memory chips (EEPROM/Flash), corroded solder joints due to moisture ingress, or failed microcontrollers and driver ICs. Such hardware faults often lead to complete loss of communication.

External factors such as voltage surges—for example, during jump-starting—or mechanical damage during removal and installation can also cause damage to the circuit board.

It’s important to note that these fault patterns can also appear in identical variants like 5Q0959655AS, 5Q0959655CD, 5Q0959655M, and 5QF959655BQ, since they share the same technical platform.

How do you recognize a defect in the 5Q0959655AQ control unit?

A defective airbag control unit 5Q0959655AQ typically manifests as a permanently illuminated airbag warning light (SRS lamp) on the dashboard. Other clear indicators include error codes stored in the fault memory, such as B2000 (“control unit defective”), or messages indicating that communication with the control unit is impossible.

The airbag warning light is the primary symptom. It may remain lit immediately after starting the engine or flash sporadically during driving, signaling an emerging fault.

During workshop diagnostics, the control unit often proves unresponsive. Diagnostic tools like VCDS or ODIS receive no reply, pointing to a serious internal malfunction or a problem with the CAN bus connection.

If error codes are still readable, entries such as “Internal Error,” “EEPROM/Flash Error,” or the specific code B2000 directly indicate a defect within the control unit that requires repair.

In which vehicles is the 5Q0959655AQ installed?

The airbag control unit 5Q0959655AQ is primarily used in Volkswagen Group vehicles built on the modern MQB platform. At Airbag24, we specialize in repairing this control unit, particularly for Audi models such as the Audi Q2 from the GA series.

At Airbag24, we offer professional repair services for the control unit with part number 5Q0959655AQ and its variants for the following models:

Audi:

Q2 (Type GA, 2016–2020)

Q2 Facelift (Type GA, from 2020 onward)

Since the part-number family (e.g., 5Q0959655AS, 5QF959655BQ) is used modularly across the VW Group, this control unit can also be found in other MQB models such as the Volkswagen Golf VII and related vehicles.

How does the repair of the 5Q0959655AQ proceed at Airbag24?

After sending your removed control unit to Airbag24, our technicians perform a comprehensive analysis. Depending on the nature of the fault, stored crash data is erased or defective electronic components on the circuit board are replaced. Following a successful functional test on the test bench, your unit is returned ready for installation, complete with 2 years’ statutory liability for defects.

The repair process at Airbag24 is designed for maximum safety and quality. We recommend reading out the fault memory before removing the control unit and including the printout with your package. Removal should only be performed by qualified technicians with the vehicle battery disconnected.

Upon receipt at Airbag24, the control unit undergoes an initial inspection. Communication is tested, and the internal memory is analyzed for crash data or hardware defects. A visual inspection of the circuit board under a microscope reveals physical damage such as corrosion or defective solder joints.

The actual repair involves either safely resetting the crash data using specialized software or professionally repairing the electronics. Defective SMD components, memory chips, or other parts are replaced in an ESD‑protected environment.

Finally, each repaired control unit undergoes a comprehensive functional test on a dedicated test bench. This ensures that all functions have been restored before the unit is shipped back to you. We provide 2 years' statutory liability for defects on every repair.