Airbag control unit with part number 77960-TFN-W820-M4

What does the airbag control unit 77960-TFN-W820-M4 do?

The airbag control unit 77960-TFN-W820-M4 coordinates the restraint system (SRS) in the Honda. Using the crash sensors it determines in an accident which airbags and seatbelt pretensioners trigger, and this happens within milliseconds.

During operation it monitors the system continuously. It indicates any faults that occur via the airbag warning light.

After an accident it stores crash data and is locked afterwards.

Why does the control unit 77960-TFN-W820-M4 fail?

Crash data from an earlier event is the most common cause, even if no airbag has deployed. Other causes are aged electronic components, moisture and corrosion, cold solder joints and voltage spikes.

Crash data remains in memory, and a normal diagnostic tool cannot erase it. It must therefore be kept in mind during every fault-finding exercise.

The other causes act independently of the accident. Components age over the years, moisture creeps into the plugs, and voltage spikes occur, for example, with a weak battery or jump start.

How can you tell that the 77960-TFN-W820-M4 is defective?

A fault shows up on the airbag warning light in the instrument cluster, which lights up permanently or intermittently. An error message may appear alongside it, the diagnostic tool may not find the control unit, or the fault memory remains.

Here the diagnostic tool provides the decisive indication when it cannot establish a connection.

While the fault exists, airbags and seatbelt pretensioners may possibly not trigger in an emergency. The warning light should therefore be taken seriously as a warning.

Which vehicles is the 77960-TFN-W820-M4 fitted in?

The 77960-TFN-W820-M4 is fitted in these vehicles: Honda Civic 10th generation (2015-2022).

This list shows the assignment in detail:

• Honda Civic 10th generation (2015-2022)

Compare the part number on the label of the removed unit with this page, so that you know for sure that you have the matching unit. However, have the fault memory read out beforehand, because only the log shows whether the control unit is defective or whether a plug or cable causes the fault.

For the same vehicles, we also repair control units with the part numbers 77960-SMG-G014-M1, 77960-TBA-A01, 77960-TBA-A02, 77960-TBA-A03, 77960-TBA-A04, 77960-TBA-A05.

How does the repair of the 77960-TFN-W820-M4 work?

First have the fault memory read out and enclose the log. Then disconnect the battery, remove the control unit and create a repair order online. Then pack the unit well and send it in.

At Airbag24 the unit is tested on the test bench, defective components are replaced, the crash data is erased and a function test is carried out. Afterwards the own unit is returned to you.

Checking, repairing and testing takes 3–4 working days at Airbag24 as a rule. The order of the first steps is mandatory for safety reasons. 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-TFN-W820-M4 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 by UPS.

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