Airbag control unit with part number 77960-TFN-W020-M4

What does the airbag control unit 77960-TFN-W020-M4 do?

The airbag control unit 77960-TFN-W020-M4 is the central control unit of the restraint system (SRS) for vehicles of the brand Honda. It measures deceleration through crash sensors, decides on triggering in an accident and monitors the system continuously. After a crash, it stores crash data and locks itself.

Triggering takes place in fractions of a second, because the restraint system is designed precisely for this. The unit reports faults via the airbag warning light in the instrument cluster.

Only the repair lifts the lock after an accident.

Why does the control unit 77960-TFN-W020-M4 fail?

Stored crash data from an earlier accident is the most common cause for the 77960-TFN-W020-M4, even if no airbag has deployed. A normal diagnostic tool cannot erase this data; Airbag24 removes it during the repair. Further causes can be aged electronics, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

An attempt to delete the data with the usual diagnostic tool fails for this reason, and the fault memory remains.

The other causes are ageing and environmental influences. Electronic components lose reliability over the years, solder joints can go cold, and moisture and corrosion attack the contacts. Voltage spikes, for example with a weak battery or a jump start, additionally stress the electronics.

Which of these causes is actually present is shown only by the check on the test bench.

How can you tell that the 77960-TFN-W020-M4 is defective?

The airbag warning light in the instrument cluster stays on at the 77960-TFN-W020-M4 permanently or only intermittently. In addition, the instrument cluster shows a fault message, a diagnostic tool gets no connection to the control unit, or the fault memory cannot be cleared.

Signs like these must be taken seriously, because the airbags and seatbelt pretensioners may not deploy in an emergency. The light reports the defect even when nothing noticeable can be felt while driving.

A missing connection to the diagnostic tool is also among the signs that justify a check.

Which vehicles is the 77960-TFN-W020-M4 fitted in?

This control unit (77960-TFN-W020-M4) is installed in these vehicles: Honda Civic 10th generation (2015-2022). The basis of the assignment is the part number of the unit.

The assignment in detail is shown in this overview:

• Honda Civic 10th generation (2015-2022)

Compare the number on the label of the removed unit with this page; that only establishes that you have the right unit. Have the fault memory read out beforehand, because the record shows whether the control unit is defective or whether a plug or cable is the cause.

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-W020-M4 work?

First, have the fault memory read out on the 77960-TFN-W020-M4 and attach the log to the unit. Then disconnect the battery, and only then remove the control unit. Next, create a repair order online and send the unit in. At Airbag24, checking, repairing and testing usually take 3–4 working days.

Airbag24 checks the unit on the test bench, repairs defective components, erases the crash data and carries out a function test. Afterwards, your own unit comes back.

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-W020-M4 get to Airbag24?

You send the 77960-TFN-W020-M4 to Airbag24 as a parcel, or you book a UPS collection for an extra charge. After the repair, Airbag24 sends the unit back by UPS.

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