B2722 - Airbag control unit not locked airbag control unit fault

What does error code B2722 mean in the airbag control unit?

Error code B2722 reports that the airbag control unit on Mercedes-Benz is not locked. The control unit has not been put into operation, so the restraint function is not enabled. This is at first not a sign of a faulty component, but of a missing work step on the control unit.

An airbag control unit must be put into operation and locked with the Mercedes-Benz diagnostic system before it enables the restraint system. If this step is missing, the control unit stores B2722 and switches on the airbag warning light. In this state the airbags and seatbelt pretensioners are not enabled.

How do you recognise error code B2722?

The airbag warning light stays on, and B2722 is stored in the fault memory. The entry can be read out with a diagnostic tool and does not disappear for as long as the commissioning of the control unit has not been completed and the unit is not locked.

Further airbag entries may also be stored in the fault memory. Whether the control unit is locked is shown by reading it out with a diagnostic tool; the warning light alone says nothing about this. A permanently stored entry is therefore not removed by clearing it.

What causes error code B2722?

With B2722, a work step in the commissioning of the control unit is missing; a component fault is at first not the main suspect. Three causes are possible: commissioning that was not carried out, locking that was not completed, or an internal fault in the unit.

• The airbag control unit was not put into operation with the Mercedes-Benz diagnostic system.
• The locking of the control unit was not completed.
• The control unit has an internal fault and therefore cannot be locked.

The first two points can be clarified at the workshop; the third only shows itself when the locking does not succeed.

In which vehicles does error code B2722 occur?

Error code B2722 is known on Mercedes-Benz, among others on the Sprinter W907 and the E-Class W213. On other vehicles the meaning may differ, and the list is not complete. What counts is the fault memory of your vehicle.

Even in these models, the meaning applies only to the control unit in question. Which state is actually present is shown by looking at the fault memory of your vehicle.

How is error code B2722 resolved?

Error code B2722 is resolved by putting the airbag control unit into operation and locking it at a Mercedes specialist workshop with the Mercedes-Benz diagnostic system. Only if that does not succeed is a test of the unit an option. First you read out the fault memory.

First have the fault memory read out with a diagnostic tool. After that, the commissioning or locking can be completed at a Mercedes specialist workshop. Work on the airbag system belongs in expert hands.

If the control unit cannot be locked or reports an internal fault afterwards, disconnect the battery and remove the unit. Create a repair order online and send the control unit to Airbag24. Checking, repairing and testing usually take 3–4 working days.

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.