Airbag control unit with part number 65.77-6977427-02

What does the airbag control unit 65.77-6977427-02 do?

The airbag control unit 65.77-6977427-02 is the control unit of the restraint system (SRS) in BMW. In a crash it assesses the signals from the crash sensors and triggers the appropriate airbags and seatbelt pretensioners.

It works in the background and continuously monitors whether all components of the system function. If it detects a fault, it indicates this with the airbag warning light.

After an accident it stores crash data and locks itself.

Why does the control unit 65.77-6977427-02 fail?

The most common cause is crash data stored after an accident, even if no airbag was triggered. A standard diagnostic tool cannot erase this data; in addition there are ageing, dry solder joints, moisture and voltage spikes.

Crash data is accident data stored in the control unit; it reveals nothing further about the condition of the electronics.

Besides the crash data, ageing electronic components count among the causes. Dry solder joints, moisture and corrosion at plug connectors, and voltage spikes from a weak battery or a jump start also belong to them. Which of these applies in an individual case only an inspection will show.

How can you tell that the 65.77-6977427-02 is defective?

A defect shows itself through a lit airbag warning light, an error message in the instrument cluster, no connection to the diagnostic tool and a fault memory that cannot be erased. Each of these signs is a reason for an inspection.

The airbag warning light in the instrument cluster stays on permanently or intermittently. While it is lit, airbags and seatbelt pretensioners may not trigger in an emergency. That is the most important reason to clarify the fault promptly.

Which vehicles is the 65.77-6977427-02 fitted in?

The airbag control unit 65.77-6977427-02 is fitted in these vehicles: BMW 3 Series E90 LCI Saloon (2008-2011), E90 Saloon (2005-2008), E91 Touring (2005-2008) and E91 LCI Touring (2008-2012).

Here are the models we have assigned to this part number:

• BMW 3 Series E90 LCI Saloon (2008-2011)
• BMW 3 Series E90 Saloon (2005-2008)
• BMW 3 Series E91 Touring (2005-2008)
• BMW 3 Series E91 LCI Touring (2008-2012)

Comparing the part number on the label of the removed unit with this page only confirms that you have the right unit. Whether the unit is defective or a cable or plug is causing the problem is shown only by the fault memory, which you should have read out before removal.

For the same vehicles, we also repair control units with the part numbers 285010062, 285010064, 285010066, 285010070, 31918443202L, 65.77-9119058-01.

How does the repair of the 65.77-6977427-02 work?

The process begins with reading out the fault memory; the log then goes with the unit. Next, disconnect the battery and remove the control unit, create a repair order online and send the packed unit. At Airbag24, inspection, repair and function testing usually take 3–4 working days.

At Airbag24 the unit goes on the test bench; defective components are repaired, stored crash data is erased and a function test is carried out. Afterwards the unit returns 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 65.77-6977427-02 get to Airbag24?

You send the unit as a parcel or book a UPS collection for an extra charge. The return journey after repair is likewise made via UPS.

A shockproof packed unit and the printed repair order belong together in the parcel.