B101A29 - Crash sensor, driver front airbag, implausible signal airbag control unit fault

What does error code B101A29 mean in the airbag control unit?

Error code B101A29 reports that the signal from the crash sensor for the driver-side front airbag is implausible. Behind the base code is the fault type. The airbag control unit stores the fault and switches on the airbag warning light.

Implausible means that the control unit does receive a signal from the crash sensor, but it does not match what the control unit expects. Because the signal cannot be trusted, this part of the restraint system cannot work reliably.

This meaning applies to Seat and Volkswagen. In the Seat Leon, the entry appears in the fault memory together with the message that the control unit itself is faulty.

How do you recognise error code B101A29?

The fault can be recognised by the permanently lit airbag warning light. With a diagnostic tool, the code is in the fault memory, and clearing it only makes it disappear temporarily.

Further entries alongside the code are possible. They help narrow down whether the sensor or the control unit itself is affected, and should be noted in full when reading out.

What causes error code B101A29?

An implausible sensor signal can come from the crash sensor itself, from the connector and wiring, or from the evaluation in the airbag control unit. The cause can only be narrowed down by checking the components.

• A crash sensor that delivers a distorted signal.
• A connector with contact resistance due to corrosion or moisture.
• Damaged wiring to the sensor.
• A defect in the evaluation electronics of the control unit, for example at old solder joints.

Crash data after an accident and voltage spikes caused by a weak battery are further possible reasons.

In which vehicles does error code B101A29 occur?

Error code B101A29 is known in the Seat Leon 3 and the Volkswagen Golf 7. The list does not claim to be complete, and in other vehicles the code may mean something different.

Whether the description applies to your vehicle is shown by the diagnosis.

How is error code B101A29 resolved?

Begin by having the fault memory read out with a diagnostic tool. Then have the crash sensor, connector and wiring checked in a specialist workshop. If the fault lies in the airbag control unit, send it in to Airbag24 for repair.

To do this, disconnect the battery, remove the control unit, create a repair order online and send the unit in. 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.

Work on the airbag system belongs in expert hands. This applies to removing the control unit just as much as to any check of connectors, wiring and sensors.