Airbag control unit with part number 31690072701C

What does the airbag control unit 31690072701C do?

The airbag control unit 31690072701C is the central control unit of the restraint system (SRS) for BMW. It evaluates the signals from the crash sensors and decides in an accident, within milliseconds, which airbags and seatbelt pretensioners are triggered.

The unit checks the system continuously and displays faults via the airbag warning light in the instrument cluster.

After an accident, it stores crash data and locks itself.

Why does the control unit 31690072701C fail?

The most frequent cause is stored crash data after an accident, even if no airbag has deployed; a normal diagnostic tool cannot erase it. Aged electronic components, cold solder joints, moisture, corrosion and voltage spikes are also possible causes.

Crash data is created when an accident is evaluated, and it remains in the unit afterwards. A diagnostic tool reads it out but does not remove it. Airbag24 erases it during the repair.

The other causes concern age and environment. Electronics age, solder joints can go cold, and moisture corrodes plug connections. Voltage spikes, for example from a weak battery or a jump start, put additional strain on the circuits.

How can you tell that the 31690072701C is defective?

The airbag warning light in the instrument cluster stays on permanently or intermittently if a defect is present on the 31690072701C. This is accompanied by fault messages in the instrument cluster, a diagnostic tool without connection and a fault memory that cannot be cleared.

The warning light makes the defect visible as soon as the control unit detects it. A fault message in the instrument cluster usually confirms this, which is why you should have the system checked promptly.

While the fault persists, airbags and seatbelt pretensioners may fail to trigger in an emergency.

Which vehicles is the 31690072701C fitted in?

The control unit 31690072701C is fitted in these vehicles: BMW 7 Series E38 (1994-1998) and E38 LCI (1998-2001); BMW M5 E39 (1998-2003); BMW 5 Series E39 (1995-2004); BMW Z8 E52 (2000-2003).

The following vehicles are assigned to this part number:

• BMW 7 Series E38 (1994-1998)
• BMW 7 Series E38 LCI (1998-2001)
• BMW M5 E39 (1998-2003)
• BMW 5 Series E39 (1995-2004)
• BMW Z8 E52 (2000-2003)

Compare the part number on the label of the removed unit with this page, so that you have the correct unit in front of you. Have the fault memory read out beforehand, because only this log shows whether the control unit is faulty or whether a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 65 77 6 919 781, 65 77 6 919 789, 65.77-6900727, 65.77-6920848, 6577-6997257, 6577-8372521.

How does the repair of the 31690072701C work?

When repairing the 31690072701C, first have the fault memory read out and enclose the log. Then disconnect the battery and only afterwards remove the control unit. Then create a repair order online and send the unit in well packed.

Airbag24 checks the unit on the test bench, replaces defective components, deletes stored crash data and carries out a functional test. Afterwards, your own unit is returned to you.

Checking, repairing and testing at Airbag24 typically take 3–4 working days.

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 31690072701C get to Airbag24?

You send the control unit 31690072701C as a parcel or book a UPS collection for an extra charge. After the repair, Airbag24 returns it to you by UPS.

Place the printed repair order in the parcel and pack the unit shockproof.