Airbag control unit with part number 98221SJ640

What does the airbag control unit 98221SJ640 do?

The airbag control unit 98221SJ640 is the control unit of the restraint system (SRS) in the Subaru. It evaluates the signals from the crash sensors and decides in an impact which airbags and seatbelt pretensioners are triggered.

While driving, the unit continuously monitors the components of the system. If it detects a fault, the airbag warning light in the instrument cluster shows it, and the entry is stored in the fault memory.

After an accident the control unit writes crash data and then locks itself. This is a protective function that decides, in an emergency, whether airbags are deployed.

Why does the control unit 98221SJ640 fail?

Stored crash data is the most common cause, even if no airbag has deployed. Other possible causes are aged electronics, cold solder joints, moisture and corrosion at plug connections, and voltage spikes from a weak battery or jump-starting.

Crash data cannot be removed with a commercially available diagnostic tool. It therefore stays in the control unit, and Airbag24 erases it as part of the repair.

The other causes are technical in nature and relate to age and environment. Electronic components lose reliability over time, solder joints can have cold faults, and moisture attacks the contacts.

How can you tell that the 98221SJ640 is defective?

Typical signs of a defect in the 98221SJ640 are an airbag warning light in the instrument cluster that stays on permanently or intermittently, and a fault message. In addition, there may be problems connecting to the diagnostic tool and a fault memory that cannot be cleared.

• airbag warning light in the instrument cluster: permanent or intermittent
• fault message in the instrument cluster
• diagnostic tool without connection to the control unit
• fault memory cannot be cleared

In that case, the airbags and seatbelt pretensioners may not deploy in an emergency. A prompt check is therefore advisable.

Which vehicles is the 98221SJ640 fitted in?

The 98221SJ640 is fitted in these vehicles: Subaru Forester SK (2018-2021) and SK Facelift (from 2021).

The list below shows the models with their years of construction.

• Subaru Forester SK (2018-2021)
• Subaru Forester SK Facelift (from 2021)

Matching the part number with the label of the removed unit only confirms that it is the correct unit. The actual question of whether the control unit is defective or whether plugs and cables are the cause is answered by the fault memory. Please have it read out before removal.

For the same vehicles, we also repair control units with the part numbers 1523004370, 98221FC210, 98221SJ000, 98221SJ001.

How does the repair of the 98221SJ640 work?

First have the fault memory read out and enclose the log in the parcel. Then disconnect the battery and only after that remove the control unit. Next, create a repair order online and send the unit in well packed.

Airbag24 checks the control unit on the test bench, repairs defective components, erases the stored crash data and carries out a function test. Afterwards the unit is returned to you.

This processing takes 3–4 working days; the time covers only testing, repair and function testing. Our repairs come with 2 years' statutory liability for defects. 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.

How does the control unit 98221SJ640 get to Airbag24?

You can send the control unit 98221SJ640 as a parcel or have it collected by UPS for an extra charge. Airbag24 sends it back to you by UPS after the repair.

Place the printed repair order in the parcel and pad the unit shock-proof.