Audi A6 C8 4AH Allroad airbag control unit repair

What is an Audi A6 C8 4AH Allroad airbag control unit?

As the central control unit of the restraint system (SRS), the airbag control unit in the Audi A6 C8 4AH Allroad coordinates all airbags and seatbelt pretensioners. It evaluates the signals from the crash sensors, determines the appropriate deployment within milliseconds in an impact and monitors the system continuously.

A unit of this kind operates in your Audi A6 C8 4AH Allroad (2019 to 2025). If it detects a fault, the airbag warning light in the instrument cluster draws attention to it.

If an accident has occurred, the unit stores crash data and locks itself.

Why is the Audi A6 C8 4AH Allroad airbag control unit defective?

In most cases the cause is crash data left behind by an accident, even if no airbag was deployed. Ageing electronic components, cold solder joints, moisture with corrosion on connectors and voltage spikes are also possible causes.

A standard diagnostic tool cannot remove stored crash data. Over the years the electronics also wear out: solder joints develop fine cracks, and moisture eats away at the contacts of the connectors. A weak battery or jump-starting can also produce voltage spikes that damage the components.

Signs of a defect are an airbag warning light that stays on permanently, a fault memory that cannot be reset, or a diagnostic tool that fails to connect.

Common error codes for Audi A6 C8 4AH Allroad airbag control unit repair

The codes for the Audi A6 C8 4AH Allroad point to internal faults of the control unit, to the power supply or to individual squib circuits of the airbags. They are read from the fault memory with a diagnostic tool.

A code can affect very different parts of the system: the control unit itself, the power supply, the squib circuits of the front and side airbags, or the wiring in between. The codes below occur on this model, each with a brief explanation.

• 65535 → General internal fault in the control unit
• 00532 → Supply voltage too low, sporadic
• 00588 → Driver airbag squib circuit, resistance fault
• 00590 → Front passenger airbag squib circuit, second stage
• 01217 → Front side airbag squib circuit, driver side, resistance fault
• 01218 → Front side airbag squib circuit, front passenger side, resistance fault

Diagnosis shows the way to clarification: read out the fault memory and keep a record of the log. A single code does not yet prove a defect in the control unit, however, as connectors, wiring or an airbag module can also be the cause. Only the inspection shows where the fault lies.

What part numbers are available for the Audi A6 C8 4AH Allroad airbag control unit repair?

The label on your control unit shows the part number, which defines its exact version. Depending on equipment and year of manufacture, the numbers differ within a model series.

You can find known part numbers for this model here; the list is not complete.

• 4N0959655AE
• 4N0959655J
• 4N0959655K
• 4N0959655Q

Compare the number on your unit with the list. This only ensures that you have the right unit in front of you. Whether a defect is present is clarified only by the fault memory readout or the inspection at Airbag24.

The process up to the repair: have the fault memory read out, disconnect the battery, remove the control unit, create a repair order online and send in the unit. Inspection, repair and testing usually take 3–4 working days at Airbag24. 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.