Airbag control unit with part number 89170-50K31

What does the airbag control unit 89170-50K31 do?

As the airbag control unit, the 89170-50K31 is responsible for the restraint system (SRS) of Lexus. It checks the signals from the crash sensors, determines in an emergency which airbags and seatbelt pretensioners are triggered, and monitors the system without a break. After an accident it stores crash data and locks itself.

If a fault is detected, the unit shows it via the airbag warning light in the instrument cluster. The decision to trigger is made within milliseconds.

Why does the control unit 89170-50K31 fail?

The most common cause of a failure of control unit 89170-50K31 is stored crash data, even if no airbag has deployed. A normal diagnostic tool does not remove this data. Other causes include aged electronics, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

After an accident the unit records crash data, regardless of whether an airbag fired. A commercially available diagnostic tool cannot erase these entries.

Aged electronic components and cold solder joints are typical weak points over the years. Moisture promotes corrosion at plug connections, and voltage spikes, for example from a weak battery or jump-starting, put stress on the electronics.

How can you tell that the 89170-50K31 is defective?

A defect in the 89170-50K31 shows up as the airbag warning light in the instrument cluster, which stays on permanently or intermittently. Fault messages also appear in the instrument cluster, the diagnostic tool cannot find the control unit, and the fault memory cannot be cleared.

While these signs persist, airbags and seatbelt pretensioners may not trigger in an emergency. The warning light therefore makes the condition visible.

Whether the control unit itself is affected or a plug is to blame can only be established by reading out the fault memory.

Which vehicles is the 89170-50K31 fitted in?

Control unit 89170-50K31 is fitted in these vehicles: Lexus LS XF50 (from 2018). The assignment refers exclusively to part number 89170-50K31.

You will find the details on the models in this list:

• Lexus LS XF50 (from 2018)

Comparing the part number on the label of the removed unit with this page only confirms that it is the right unit. Have the fault memory read out beforehand. Only the result shows whether the control unit is defective or whether plugs or cables are the cause.

For the same vehicles, we also repair control units with the part numbers 89170-50K81, 89170-50K83, 89170-50L00, 89170-50L03, 89170-53790, 89170-53820.

How does the repair of the 89170-50K31 work?

The process begins with reading out the fault memory; you enclose the log. Only then do you disconnect the battery and remove control unit 89170-50K31. Finally, you create a repair order online and pack the unit securely for dispatch.

At Airbag24 the unit is checked on the test bench, defective components are repaired, crash data is erased and a function test is carried out. Processing there usually takes 3–4 working days. Your own unit is then sent back to you.

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 89170-50K31 get to Airbag24?

You send control unit 89170-50K31 as a parcel or book a UPS collection for an extra charge. Airbag24 returns the repaired unit by UPS.

Put the printed repair order in the parcel, and pack the unit so that it is shock-resistant.