Airbag control unit with part number 77960-TM8-J420-M2

What does the airbag control unit 77960-TM8-J420-M2 do?

The airbag control unit 77960-TM8-J420-M2 forms the central control unit of the restraint system (SRS) of Honda. It evaluates the signals from the crash sensors, decides in a crash whether airbags and seatbelt pretensioners are triggered, and monitors the system continuously.

If it detects a fault, it reports this via the airbag warning light. After an accident, the unit stores crash data and locks itself.

Why does the control unit 77960-TM8-J420-M2 fail?

The most common cause is crash data stored after an accident, even if no airbag was triggered. A normal diagnostic tool cannot erase this data. Other causes include aged electronics, cold solder joints, moisture, corrosion and voltage spikes.

The unit creates crash data as soon as it registers a crash event, regardless of whether an airbag triggers. Aged components and cold solder joints affect the electronics over a longer period, while moisture and corrosion attack the contacts at plug connections. Voltage spikes, for example from a weak battery or when connecting jump leads, place additional stress on the electronics.

How can you tell that the 77960-TM8-J420-M2 is defective?

The airbag warning light in the instrument cluster lights up permanently or intermittently, a fault message appears in the instrument cluster, and the fault memory cannot be cleared. The diagnostic tool also fails to establish a connection with the control unit.

As long as this finding persists, airbags and seatbelt pretensioners may not trigger in an emergency, so the warning must not be ignored. A light that only comes on intermittently should also be checked.

Which vehicles is the 77960-TM8-J420-M2 fitted in?

The information refers to Honda. The control unit 77960-TM8-J420-M2 is fitted in these vehicles: Honda Insight 2nd generation (2009-2014).

The stored vehicles at a glance:

• Honda Insight 2nd generation (2009-2014)

Compare the part number on the label of the removed unit with the number on this page; this only confirms that it is the correct unit. Also have the fault memory read out beforehand, because only this result shows whether the control unit is defective or whether a plug or a cable is the cause.

For the same vehicles, we also repair control units with the part numbers 77960-TM8-A01, 77960-TM8-A020-M2, 77960-TM8-A03.

How does the repair of the 77960-TM8-J420-M2 work?

First have the fault memory read out, enclose the log, disconnect the battery and remove the control unit. Then 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, replaces defective components, erases stored crash data and carries out a function test. The repaired unit is then returned to you.

This time covers only the checking, repairing and testing at Airbag24 and has nothing to do with your steps or the shipping. 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 77960-TM8-J420-M2 get to Airbag24?

You send the unit in as a parcel or book a UPS collection for an extra charge. After the repair, Airbag24 sends it back to you via UPS.

Put the printed repair order into the parcel and pack the unit shock-resistant.