Airbag control unit with part number 89170-78220

What does the airbag control unit 89170-78220 do?

The airbag control unit 89170-78220 coordinates the restraint system (SRS) of Lexus in the vehicle. It polls the crash sensors, determines in an impact which airbags and seatbelt pretensioners are triggered, and checks the system continuously during operation. After an accident it stores crash data and locks itself.

A crash unfolds in a fraction of a second, so the unit makes its decision without asking. If it finds a fault in the system, it reports it to the driver via the airbag warning light in the instrument cluster.

Why does the control unit 89170-78220 fail?

Crash data stored after an accident is the most frequent cause, even if no airbag has deployed; a normal diagnostic tool cannot erase it. Airbag24 erases it during the repair. Ageing components, cold solder joints, moisture and corrosion at plug connections and voltage spikes also contribute.

The crash data is the most frequent cause because it stays in memory after every event that the unit has registered.

• ageing electronic components
• cold solder joints in the circuit
• moisture and corrosion at plug connections
• voltage spikes, for example from a weak battery or jump-starting

Which of these causes applies is determined by reading the fault memory together with an examination of the unit.

How can you tell that the 89170-78220 is defective?

A defect shows mainly as the airbag warning light in the instrument cluster staying on constantly or lighting up intermittently. In addition there are error messages in the instrument cluster, no connection to the diagnostic tool, and a fault memory that cannot be cleared. In an emergency, airbags and seatbelt pretensioners may then fail to trigger.

• Airbag warning light stays on constantly or lights up intermittently
• Error message in the instrument cluster
• Diagnostic tool does not find the control unit
• Fault memory cannot be cleared

Note which signs occur and since when, before you create a repair order.

Which vehicles is the 89170-78220 fitted in?

The control unit 89170-78220 is fitted in these vehicles: Lexus NX AZ20 (from 2021).

The following overview shows the vehicles to which Airbag24 assigns this part number.

• Lexus NX AZ20 (from 2021)

Compare the part number on the label of the removed unit with this page. That only tells you that you have the right unit in front of you. Have the fault memory read out beforehand, because only the log 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-F6010.

How does the repair of the 89170-78220 work?

Processing, repair and function test at Airbag24 usually take 3–4 working days. Beforehand, have the fault memory read out and attach the log, then disconnect the battery and remove the control unit.

Then create a repair order online and send in the unit well packed. This time applies only to the work at Airbag24, not to your steps before it.

Airbag24 checks the unit on the test bench, replaces defective components, erases stored crash data and carries out a function test. Afterwards your own unit is 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 89170-78220 get to Airbag24?

You send the unit to Airbag24 as a parcel or book a UPS collection for an extra charge. After the repair Airbag24 returns it to you by UPS.

Put the printed repair order into the parcel, and pack the control unit shock-proof.