Audi RS4 B7 8H Convertible airbag control unit repair

What is an Audi RS4 B7 8H Convertible airbag control unit?

If an accident occurs in the Audi RS4 B7 8H Convertible, the airbag control unit decides within milliseconds which airbags and which seatbelt pretensioners fire. It is the control unit at the heart of the restraint system (SRS) and monitors the entire system during normal driving as well.

To this end, the crash sensors deliver their measured values at the moment of impact. The control unit evaluates these signals and releases only the deployment that suits the situation. It is installed in the Audi RS4 B7 8H Convertible (2007 to 2008); it comes from Bosch.

Between deployments it constantly checks itself and all connected components. If it finds a fault, the airbag warning light in the instrument cluster reports this immediately. If it has registered an accident, it stores crash data and locks itself.

Why is the Audi RS4 B7 8H Convertible airbag control unit defective?

The most common cause is crash data that remains in the unit after an accident, even if no airbag was deployed. Ageing components, cold solder joints, corrosion and moisture in the connectors, or voltage spikes may also be the cause.

An ordinary diagnostic tool cannot remove this crash data. Even after the accident damage to the vehicle has been repaired, the unit therefore remains in a fault state.

Without an accident, other causes are at play: electronic components age, solder joints crack over time, and corrosion together with moisture attacks the connectors. A weak battery or jump-starting can also produce voltage spikes that damage the electronics.

How to recognise a defect: the airbag warning light stays on continuously, the fault memory stays filled despite attempts to clear it, or the diagnostic tool cannot make contact with the control unit. In that case, we recommend a diagnosis first, before you take any further steps.

Common error codes for Audi RS4 B7 8H Convertible airbag control unit repair

The codes for this unit indicate faults in the control unit itself, in the power supply and in the squib circuits of the airbags. Which of them occurs depends on the type of damage.

These codes are known for the airbag control unit in the Audi RS4 B7 8H Convertible, each with its meaning:

• 65535 → General internal control unit fault
• 00532 → Supply voltage temporarily too low
• 00588 → Driver airbag squib circuit, resistance fault
• 00590 → Passenger airbag squib circuit, fault
• 01217 → Front side airbag squib circuit, driver side, resistance fault
• 01218 → Front side airbag squib circuit, passenger side, resistance fault

Fault codes are read out with a diagnostic tool. However, a single code does not reliably prove that the control unit is defective; an airbag module, a connector or a wire can equally be the cause. Only during the inspection does the actual source of the fault become clear.

What part numbers are available for the Audi RS4 B7 8H Convertible airbag control unit repair?

You will find the part number on the label of the control unit; it defines the exact version. Depending on equipment and year of manufacture, different numbers occur within the same model series.

These numbers are known, among others, although the list need not be complete:

• 8H0959655D (Bosch)
• 8H0959655E (Bosch)
• 8H0959655F

Compare the number of your unit with this list. This merely ensures that it is the matching unit; whether it is defective only becomes clear from reading out the fault memory or from the inspection.

The route to repair: first you read out the fault memory, then you disconnect the battery and remove the control unit. Afterwards you create a repair order online and send the unit to us. For inspecting, repairing and testing, Airbag24 usually allows 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.