B1679 airbag control unit fault

What does error code B1679 mean?

Error code B1679 indicates a specific electrical fault in the airbag system, defined as “short circuit at the panic alarm input to battery.” The airbag control unit (SRS module) has detected an incorrect electrical connection in the panic alarm circuit. This results in the error being stored and the warning light illuminating.

Electronically, this means that the input pin on the control unit responsible for the panic alarm signal has an unwanted, permanent connection to the positive battery voltage. Such a short circuit prevents the proper functioning of this monitoring circuit and is classified by the system as a critical fault.

The panic alarm input is an integral part of the safety concept in certain vehicle models and is monitored by the airbag control unit. Therefore, maintaining the integrity of this circuit is crucial for the overall system’s reliable operation.

How do you recognize error B1679?

The primary and unmistakable symptom of error code B1679 is a permanently illuminated airbag warning light on the instrument panel. After reading the fault memory with an appropriate diagnostic tool, code B1679 appears as a specific entry pointing to the panic alarm input. Other functional failures are usually not directly noticeable.

The SRS warning light remains active after starting the vehicle and does not extinguish after a few seconds as usual. This alerts the driver to a malfunction in the restraint system, potentially preventing the airbags from deploying correctly—or at all—in the event of a crash.

A diagnosis via the OBD interface is essential to clearly identify error code B1679. Without reading the fault memory, it is impossible to accurately determine the cause based solely on the illuminated warning light.

What causes B1679?

The main cause of B1679 is a physical short circuit in the panic alarm wiring. Common triggers include damaged cable insulation, defective sensors or switches, and water ingress into connectors leading to corrosion. Faulty relays, fuses, or improper wiring after repairs can also result in this error.

A short circuit in the wiring is the most frequent source of the problem. Frayed cables that come into contact with the vehicle body or another live wire can route battery voltage directly to the control unit’s signal input.

Defective components such as switches or sensors within the panic alarm system may exhibit internal short circuits. Similarly, moisture entering connector joints can form conductive bridges between pins through corrosion.

In rarer cases, the fault may originate directly within the airbag control unit itself if an internal component on the circuit board is defective and causing the short circuit.

In which models does error B1679 occur?

Error code B1679 is particularly common in vehicles manufactured by the PSA Group. At Airbag24, we specialize in repairing this fault primarily for the first-generation Citroën C4. Although the code can appear in other brands as well, it is especially characteristic of these specific models.

At Airbag24, repairs for this error are prioritized for the following models:

Citroën C4 I (model years 2004–2008)

Citroën C4 I Facelift (model years 2008–2010)

The precise definition of the error code may vary depending on the manufacturer and control unit generation; however, for the aforementioned Citroën models, the association with the panic alarm input is clear.

How is error code B1679 professionally repaired?

Professional repair of error B1679 at Airbag24 focuses on eliminating the hardware cause within the control unit. Upon receipt, the device is analyzed at the circuit board level to locate the short circuit. Defective electronic components are expertly replaced to restore full functionality.

The process begins after removing the control unit from the vehicle and sending it to Airbag24. It is advisable to inspect the external wiring connected to the panic alarm system before removal to rule out faults outside the control unit.

Laboratory diagnostics are performed with precision. Our technicians conduct visual inspections and use measuring instruments such as multimeters to examine the panic alarm input circuit and pinpoint the exact location of the short circuit. This may involve identifying faulty resistors, capacitors, or other ICs on the board.

Subsequently, hardware repair takes place, replacing the identified defective components. If crash data was additionally recorded after an accident, it will be erased during the same procedure. Following successful repair and a final functional test, the control unit is fully operational again. We provide 2 years' statutory liability for defects on all repairs.