Volvo S90 964 airbag control unit repair

What is a Volvo S90 964 airbag control unit?

In everyday use, the airbag control unit of the Volvo S90 964 works quietly in the background: as the central control unit of the restraint system (SRS), it runs a self-test at start-up and then monitors the system continuously. It reports faults via the airbag warning light.

It also evaluates the signals from the crash sensors. In an accident, it decides within milliseconds which airbags and seatbelt pretensioners deploy. The control unit is fitted in the Volvo S90 964 (1996 to 1998). It is made by Bosch.

If the warning light comes on briefly when the ignition is switched on and then goes out, the self-test has not found a fault. After an accident, the control unit stores crash data and locks itself.

Why is the Volvo S90 964 airbag control unit defective?

The most common cause is an accident: the airbag control unit stores crash data even if no airbag has deployed, and these cannot be erased with an ordinary diagnostic tool. Other possible causes are aged electronic components, cold solder joints, moisture and corrosion at the connectors, and voltage spikes.

In the Volvo S90 964, a defect usually shows itself in the airbag warning light staying on permanently. Often the fault memory cannot be cleared, or the diagnostic tool cannot connect to the control unit at all.

Voltage spikes occur, for example, with a weak battery or when jump-starting. Electronic components also age over the years, and solder joints can become brittle through temperature changes and vibration. Moisture that reaches the connectors leads over time to corrosion and thus to contact resistance.

Common error codes for Volvo S90 964 airbag control unit repair

The fault codes for the Volvo S90 964 mainly point to internal control unit faults, communication faults on the data bus, a supply voltage that is too low and faults in the squib circuit. Which codes are in the fault memory depends on the type of fault.

Known codes for this vehicle:

• SRS-CFFF → Control unit: internal fault
• SRS-0001 → Internal functional fault in the control unit
• SRS-00D0 → Control unit: incorrect configuration
• SRS-00D5 → Communication fault with the SRS control unit
• U0151-00 → Data bus: SRS control unit not responding
• U0452-41 → Invalid data received from the SRS control unit
• SRS-0005 → Supply voltage too low
• SRS-0115 → Driver airbag squib circuit open or short circuit

Fault codes are read out with a diagnostic tool. A code alone does not reliably show that the control unit is defective. Connectors, wiring or an airbag module can also be the cause, which is why only the inspection establishes the actual fault.

What part numbers are available for the Volvo S90 964 airbag control unit repair?

The part number is on the label of the control unit. It determines the exact version, because within one model series there are different numbers depending on equipment and year of manufacture.

The following list gives known part numbers for the Volvo S90 964; it makes no claim to completeness.

• 9148338
• 9148497

Compare the number on your unit with this list. This only ensures that it is the right unit. Whether it is defective is shown only by reading out the fault memory or by the inspection.

The route to repair is short: have the fault memory read out, disconnect the battery and remove the control unit. Then create a repair order online and send the unit in. Processing at Airbag24 usually takes 3–4 working days and covers inspection, repair and testing.

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.