Airbag control unit with part number 89170-42B90

What does the airbag control unit 89170-42B90 do?

The airbag control unit 89170-42B90 is the central control unit of the restraint system (SRS) of Toyota. It evaluates the crash sensors, decides in a crash within milliseconds about airbags and seatbelt pretensioners, and monitors the system continuously. After an accident it stores crash data and locks itself.

The device reports faults via the airbag warning light in the instrument cluster. Monitoring runs for as long as the vehicle has power.

In everyday use this work remains invisible. Only a warning makes it noticeable.

Why does the control unit 89170-42B90 fail?

The most common cause is crash data stored after an accident, even without a triggered airbag. A normal diagnostic tool cannot erase them. Other causes are aged electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes, for example from a weak battery or jump-starting.

Crash data are created when the device records the impact. They remain stored until they are deliberately erased and can burden the fault memory even when nothing can be seen on the vehicle.

The other causes tend to develop gradually. An ageing component can distort signals long before a complete failure occurs.

How can you tell that the 89170-42B90 is defective?

A defect in the 89170-42B90 shows up as the airbag warning light in the instrument cluster lighting up permanently or intermittently. A fault message in the instrument cluster, no connection to the diagnostic tool or a fault memory that cannot be cleared also point to it.

A diagnostic tool without a connection to the control unit does not automatically mean that the control unit is defective. The cause may just as well be in the wiring or the plug.

While the finding persists, airbags and seatbelt pretensioners may not trigger in an emergency. Do not ignore the warning light; have it checked.

Which vehicles is the 89170-42B90 fitted in?

The control unit 89170-42B90 is fitted in these vehicles: Toyota bZ4X XC10 (2022-2025) and XC10 Facelift (from 2025).

The overview shows the vehicles recorded for this part number:

• Toyota bZ4X XC10 (2022-2025)
• Toyota bZ4X XC10 Facelift (from 2025)

Compare the part number on the label of your removed unit with this page. This only confirms that you have the right unit. Also have the fault memory read out before you remove the unit, because only this result shows whether the control unit itself is defective or whether a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 89170-42B60, 89170-42E70.

How does the repair of the 89170-42B90 work?

You first have the fault memory read out and attach the log. Then disconnect the battery and only afterwards remove the control unit 89170-42B90. Next create a repair order online and send in the well-packed unit. Processing at Airbag24 usually takes 3–4 working days.

Airbag24 checks the unit on the test bench, repairs defective components, erases the stored crash data and carries out a function test. Afterwards your own unit is returned 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 89170-42B90 get to Airbag24?

You send the control unit 89170-42B90 as a parcel or book a UPS collection for an extra charge. After the repair Airbag24 returns it by UPS.

Put the printed repair order into the parcel and pack the unit shockproof.