Audi S4 B6 8H Convertible airbag control unit repair

What is an Audi S4 B6 8H Convertible airbag control unit?

The airbag control unit in the Audi S4 B6 8H Convertible is the central control unit of the restraint system (SRS). It evaluates the signals from the crash sensors, decides within milliseconds in an accident whether airbags and seatbelt pretensioners deploy, and continuously monitors the whole system.

So that the restraint system reacts reliably in an emergency, the control unit constantly checks its own functions and those of the connected components in the background, such as the sensors and the squib circuits. If it detects a deviation, it alerts you via the airbag warning light. The control unit is installed in the Audi S4 B6 8H Convertible (2004 to 2005) as part of the restraint system.

In an accident, the control unit stores crash data and locks itself.

Why is the Audi S4 B6 8H Convertible airbag control unit defective?

The most common cause of a defective Audi S4 B6 8H Convertible airbag control unit is crash data stored after an accident, even if no airbag deployed at all. Other causes are corrosion and moisture at connectors, cold solder joints, aged electronics and voltage spikes.

An ordinary diagnostic tool cannot reach this stored crash data and cannot delete it. That is why the problem persists, even though the sensors, wiring and airbags themselves may be undamaged.

But even without an accident the electronics change over the years: components lose their properties, solder joints turn cold, and moisture makes contacts corrode. A weak battery or a jump start can also produce voltage spikes that stress sensitive circuits.

How you notice a fault: the airbag warning light stays on permanently, the fault memory cannot be cleared, or the diagnostic tool cannot establish a connection to the control unit.

Common error codes for Audi S4 B6 8H Convertible airbag control unit repair

The error codes on the Audi S4 B6 8H Convertible relate to the power supply, the squib circuits of the driver and front passenger airbags, and internal faults of the control unit. They narrow down which part of the restraint system the fault lies in.

These error codes are read out time and again in connection with the Audi S4 B6 8H Convertible airbag control unit, each shown here with its short meaning:

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

The codes are read out with a diagnostic tool. However, a single code does not allow a reliable conclusion that the control unit is defective, as a fault in connectors, wiring or an airbag module is just as possible. Only the inspection clarifies which cause applies.

What part numbers are available for the Audi S4 B6 8H Convertible airbag control unit repair?

You will find the part number on the label of your control unit, and it determines the exact version. Depending on equipment and year of manufacture, the numbers also differ within the Audi S4 B6 8H Convertible model series.

No list of numbers is stored for this model. Please read the number from the label yourself and enter it in the repair order, so that your unit is matched to the correct version.

The number alone says nothing about a defect. That is clarified by reading out the fault memory and the inspection that follows.

The way to the repair: first have the fault memory read out. Then disconnect the battery from the vehicle electrical system and remove the control unit. Create a repair order online and send the unit to us. At Airbag24, checking, repairing and testing usually take 3–4 working days.

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.