B1694 - Supply voltage too low airbag control unit fault

What does error code B1694 mean in the airbag control unit?

The error code B1694 reports a supply voltage that is too low, so the power supply to the airbag control unit in the restraint system (SRS), which it needs in order to function, is affected. The airbag control unit stores this fault and switches on the airbag warning light, so that you can see the condition in the vehicle straight away.

Once the voltage falls below the required value, the control unit records this condition as a fault. The supply voltage is the basis on which the control unit works, and it must remain sufficiently high during operation.

How do you recognise error code B1694?

You recognise error code B1694 by the airbag warning light staying on permanently and the code being stored in the fault memory. This entry cannot be permanently deleted, and it is read out with a diagnostic tool that makes the fault memory visible, so that the cause can be narrowed down.

The warning light alone does not reveal the cause. Only the code once read out shows that the supply voltage of the airbag control unit is too low.

What causes error code B1694?

Possible causes of error code B1694 include a weak or ageing battery, connectors and wiring of the power supply, and the airbag control unit itself, depending on where the voltage drops. A contact resistance or corrosion at connectors and wiring can lower the voltage at the control unit just as a weak battery can.

• A weak or ageing battery may supply too little voltage.
• A connector in the power supply may have a contact resistance or be damaged by corrosion.
• A wire in the power supply may be broken, chafed or corroded.
• The airbag control unit itself may be faulty, for example due to ageing electronic components or solder joints.

Which cause applies is shown only by testing the battery, the connectors and wiring, and the control unit.

In which vehicles does error code B1694 occur?

Error code B1694 occurs in BYD vehicles, including the models Atto 2, Atto 3, Dolphin, Dolphin Surf, Han, Seal 6, Sealion 7 and Tang. BYD is the only brand for this code, and the models listed are a selection from the known vehicles.

On other vehicles the meaning may differ, and the list is not complete.

How is error code B1694 resolved?

Error code B1694 is resolved by first having the fault memory read out with a diagnostic tool and then narrowing down the cause. If the cause lies in the power supply, have the battery, connectors and wiring checked first at a specialist workshop; if it lies in the control unit, the mail-in repair process applies.

In doing so, the voltage at the connections is checked before the control unit is considered. Work on the airbag system belongs in qualified hands.

If the cause lies in the control unit itself, disconnect the battery first and then remove the control unit. Create a repair order online and send the device to us. 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.