Airbag control unit with part number 5Q0 959 655 AK

What is the function of the Airbag Control Unit 5Q0 959 655 AK?

The Airbag Control Unit 5Q0 959 655 AK is the central control module for the Occupant Restraint System (SRS) in vehicles based on the MQB platform, such as the Škoda Superb 3V. It processes data from crash sensors and determines whether to deploy airbags and seatbelt pretensioners, thereby protecting vehicle occupants in the event of a collision.

As an MQB module, it communicates via the CAN bus with other critical control units, including the instrument cluster, engine control unit, and ABS. This interconnectedness ensures that all relevant vehicle data are factored into safety decisions.

The hardware is manufactured by various suppliers—such as Continental, TRW, or Autoliv—depending on the specific variant, and belongs to the 5Q0 959 655 series, which includes different suffixes (e.g., AA, BH, AK) to denote varying equipment levels and revisions.

Why does the Control Unit 5Q0 959 655 AK fail?

The most common cause of failure for the 5Q0 959 655 AK control unit is the storage of crash data following a collision. Other frequent issues include internal electronic faults caused by voltage spikes, moisture ingress, or aging components, manifesting as memory errors or communication problems.

A key reason for failure is the permanent retention of crash events in the internal EEPROM/Flash memory. These stored data cannot be erased through standard OBD diagnostics, effectively locking the control unit out of service—even if the airbags were not deployed.

Frequent fault codes such as “Internal Control Unit Error,” “Control Module Faulty,” or “Internal Control Module Memory Error” indicate defects within the internal electronics. Possible causes include faulty voltage regulators, defective driver stages for ignition circuits, or corrupted memory contents.

External factors like undervoltage or overvoltage due to a weak battery, jump-start procedures, or a failing alternator can damage the sensitive electronics. Additionally, since the control unit is often mounted in the center tunnel near the vehicle floor, moisture ingress may lead to corrosion on the circuit board and connector contacts.

How do you recognize a defect in the Control Unit 5Q0 959 655 AK?

A malfunction of the Airbag Control Unit 5Q0 959 655 AK primarily manifests as the airbag warning light remaining constantly illuminated in the instrument cluster. Furthermore, the control unit may no longer respond to diagnostic tools, or it may report persistent error messages such as “Crash Data Stored,” which cannot be cleared.

The clearest symptom is the persistently lit red SRS warning light. It fails to extinguish after starting the engine, signaling a serious, safety-critical issue within the airbag system.

During workshop diagnostics, fault memory entries such as “Crash Data Stored” or “Internal Error” will appear. Attempts to clear these errors via the OBD interface typically fail because the control unit is internally locked.

In some cases, the control unit becomes completely offline and stops responding to diagnostic equipment altogether. This suggests a severe internal electronic failure, possibly involving the power supply or the communication processor.

In which vehicles is the Control Unit 5Q0 959 655 AK installed?

The Airbag Control Unit 5Q0 959 655 AK is predominantly used in the third-generation Škoda Superb (Type 3V). At Airbag24, this MQB module is professionally repaired for various trim levels and model years of the Superb Mk3, restoring full functionality to the safety system.

At Airbag24, repairs for the 5Q0 959 655 AK control unit are available for the following models:

Škoda: Superb 3 [3V] (2015–2019), Superb 3 [3V] Facelift (2019–2023), Superb Combi Mk3, Superb Sportline Mk3, Superb L&K Mk3, Superb GreenLine Mk3

How is the Control Unit 5Q0 959 655 AK professionally repaired?

Professional repair at Airbag24 involves electronic refurbishment of the original control unit. After removal and shipment, the module undergoes laboratory testing, crash data is reset at the hardware level, and defective electronic components—such as voltage regulators or driver ICs—are replaced. Final tests confirm proper functionality.

The process begins with vehicle diagnostics and careful removal of the control unit, ideally accompanied by a detailed fault report. The device should be sent to the repair facility unopened.

Upon receipt at Airbag24, a thorough laboratory analysis is performed. Technicians inspect the circuit board for visible damage, such as corrosion, and conduct electrical measurements. The internal memory is read to analyze crash data and software versions.

The core repair involves selectively erasing the crash data directly from the memory chip, restoring the control unit to a fault-free state. For internal faults, defective SMD components are identified and replaced with new, equivalent parts.

Following the repair, the control unit is tested on a test bench to simulate the correct operation of all ignition circuits and sensor inputs. Two years' statutory liability for defects is provided for every repair performed.