Airbag control unit with part number K123 57K30 B

What is the function of the Airbag Control Unit K123 57K30 B?

The Airbag Control Unit K123 57K30 B is the central control unit for the passive safety system (SRS) in the Mazda CX-5 KF series. It analyzes data from the acceleration sensors to precisely deploy airbags and seatbelt pretensioners in the event of a crash. Additionally, it continuously monitors the functionality of all connected SRS components.

The primary task of this unit is the ongoing monitoring of the entire Supplemental Restraint System (SRS). It ensures that all sensors, airbag modules, and seatbelt pretensioners are operational and, in case of a malfunction, immediately activates the airbag warning light to alert the driver.

In the event of a collision, the control unit determines within milliseconds which restraint systems need to be deployed. This decision is based on data from crash sensors, which detect the force and direction of the impact and transmit this information to the control unit.

Why does the K123 57K30 B control unit fail?

A failure of the K123 57K30 B control unit is often caused by issues in the peripheral circuitry, such as broken wiring or faulty connectors linking to the SRS components. Another common cause is the storage of crash data in the internal memory after an accident, which can block further functionality.

The most frequent sources of failure are physical in nature and typically lie within the vehicle’s wiring harness. During diagnostics, technicians often identify broken or damaged wires that disrupt communication between the control unit and the sensors or airbags.

Loose or corroded connectors are equally critical. A poor connection can lead to intermittent malfunctions or complete loss of communication, often indicated by a constantly illuminated airbag warning light.

Following an airbag deployment, so‑called “crash data” is stored in the control unit’s internal memory. This is a safety measure designed to prevent reuse without professional inspection until the data has been professionally erased.

It is crucial to note that after an actual accident in which airbags have deployed, the control unit must always be replaced with a new part for safety reasons. This ensures full system functionality in the event of a subsequent collision.

How do you recognize a defect in the K123 57K30 B?

A defect in the K123 57K30 B control unit primarily manifests as a permanently illuminated airbag warning light on the instrument panel. Often, a diagnostic tool can no longer establish communication with the control unit, or specific fault codes are read out that directly indicate an internal malfunction.

The most obvious and unmistakable sign is the activated airbag warning light. It does not extinguish after starting the vehicle and signals a serious issue within the safety system that requires immediate attention.

Another clear symptom is the lack of communication with the control unit. When attempting to read the fault memory using a diagnostic device, the system reports that no connection can be established with the airbag module.

If fault codes are retrieved, they often point directly to the underlying cause. Typical entries relate to internal control unit errors, communication problems with sensors, or the aforementioned stored crash data.

In which vehicles is the K123 57K30 B control unit installed?

The airbag control unit with part number K123 57K30 B is specifically designed for the Mazda CX-5 KF series. At Airbag24, this component is repaired for models from the 2017 model year onward, including the facelift introduced in 2021, to restore full functionality of the safety system.

At Airbag24, professional repair services for the K123 57K30 B control unit are offered for the following Mazda models:

Mazda CX-5 (KF series, 2017–2021)

Mazda CX-5 (KF series facelift, 2021–present)

How does the repair of the K123 57K30 B proceed at Airbag24?

At Airbag24, the repair process for the K123 57K30 B begins with a detailed incoming inspection, during which the fault memory is read out. Depending on the diagnosis, stored crash data is erased or electronic faults are corrected. Finally, a functional test is performed to ensure full operational readiness.

After submitting the removed control unit to Airbag24, a professional diagnosis is carried out. Technicians use specialized diagnostic equipment to pinpoint the exact cause of the fault—whether it’s a hardware defect or a lockout due to crash data.

The repair scope varies depending on the findings: erasing crash data, repairing circuit traces, or replacing defective components. Additional services may include clearing fault codes and calibrating ADAS systems.

All repairs are performed to the highest standards and come with 2 years’ statutory liability for defects on the work carried out. Once installed, the repaired control unit is typically ready for immediate use (Plug & Play).