B1690 airbag control unit fault

What does error code B1690 mean?

Error code B1690 indicates a software fault directly within the airbag control unit. This points to an issue with the module’s internal software, such as an outdated version, a programming error following intervention, or incompatibility. As a result, the control unit can no longer reliably perform its safety‑critical functions, leading to deactivation of the airbag system.

Technically speaking, the control unit fails its internal self‑test because software integrity is no longer assured. This fault is not caused by an external sensor or a cable break; it lies exclusively in the control unit’s own logic.

Such a software error may occur after a crash, improper repair, or due to aging of the memory chips, which leads to corruption of the software data. For safety reasons, the system then switches into fault mode.

How do you recognize error B1690?

The primary symptom of error B1690 is a continuously illuminated or intermittently flashing airbag warning light (SRS) on the instrument cluster. Often, error code B1690 can be read from the fault memory but cannot be permanently cleared. In some cases, communication with the control unit via a diagnostic tool is disrupted or completely impossible.

The persistently lit SRS warning light is the clearest indication to the driver that the vehicle’s passive safety system is not operational. In the event of a crash, the airbags and seatbelt pretensioners would fail to deploy.

Another characteristic is that, after being cleared with a diagnostic tool, error code B1690 usually reappears immediately. This confirms that it is a permanent, internal fault within the control unit that cannot be resolved by a simple reset.

Occasionally, the control unit may become completely unreachable for diagnostic tools. The module no longer responds to requests via the diagnostic interface, making troubleshooting more challenging.

What causes B1690?

The main cause of B1690 is a software problem in the airbag control unit. This could be faulty or outdated software, a missing yet required update, or a programming error that arises after a repair or accident. Incompatibility following the replacement of vehicle components can also trigger this error.

Faulty or outdated software is one of the most common causes. The program code in the control unit contains an error or is no longer compatible with other vehicle systems, resulting in this specific error code.

A programming error may occur after a crash or repair to the airbag system. For example, if components are replaced but not properly configured in the control unit’s software, this can lead to error B1690.

Another cause is incompatibility after retrofitting or replacement. If a part is installed that does not match the software version of the airbag control unit, the system recognizes this as a critical fault.

Which vehicles are affected by B1690?

Error code B1690 occurs in a range of specific vehicle models from various premium and mass-market manufacturers. Affected models include those from Mercedes-Benz, Porsche, Toyota, Lexus, Lamborghini, and Chevrolet. Precise identification is crucial for successful diagnosis and repair.

At Airbag24, we repair error B1690 for the following models and series:

Chevrolet: Camaro Z/28 (2nd generation)

Lamborghini: Huracán LP580-2 (2015–2020)

Lexus: LS LS460L

Mercedes-Benz: GLC SUV X253 (2015–2022)

Porsche: 911 Carrera S 991

Toyota: Avensis T270 (2008–2018, including facelifts—T270 1st facelift 2011–2015 and T270 2nd facelift 2015–2018), Avensis Sedan

How is error B1690 professionally repaired?

Professional repair of error B1690 focuses on the software level of the removed airbag control unit. Following a thorough diagnosis, faulty or outdated device software is updated and corrected. If crash data has been stored after an accident, this data is also erased. Final functional tests ensure full operability.

After sending the removed control unit to Airbag24, a detailed analysis is first conducted to identify the exact cause of the software fault. For this purpose, the device is read using specialized test benches.

The core of the repair involves replacing the faulty software on the control unit with a correct, up-to-date version. This is accomplished through a process known as “flashing,” where the program data is rewritten onto the module’s memory chips.

If the fault occurred as a result of an accident, the stored crash data will also be erased. This data often prevents the control unit from functioning normally and must be removed to reset the module.

After software correction, each control unit undergoes a comprehensive functional test. Only when all parameters are correct and no further errors are reported is the repair considered complete. The unit can then be reinstalled in the vehicle as a “plug-and-play” solution. We provide a 12-month warranty on all repairs.