Airbag control unit with part number 39790-SZ3-003

What is the function of Airbag Control Unit 39790-SZ3-003?

The airbag control unit with part number 39790-SZ3-003 is the central control module for the passive safety system in the first-generation Honda Legend. Its primary task is to continuously process data from crash sensors and, in the event of a collision, precisely and instantaneously deploy the airbags and seatbelt pretensioners.

As the “brain” of the restraint system, this module constantly monitors the operational readiness of all connected components, including the front airbags, seatbelt pretensioner systems, and the acceleration sensors distributed throughout the vehicle.

The internal electronics are specifically designed to match the vehicle architecture of the Honda Legend models produced between 1985 and 1990. Proper functionality is critical for occupant safety, as any malfunction could render the entire airbag system inoperable.

What types of failures occur in control unit 39790-SZ3-003?

The most common cause for repair is the storage of crash data after an accident, which locks the control unit. Other typical issues include internal hardware faults that result in non‑erasable fault codes, as well as physical damage to the CAN‑bus connector due to corrosion or water ingress, disrupting communication.

After deploying airbags or seatbelt pretensioners, a permanent entry is recorded in the control unit’s memory. This “crash log” locks the module for safety reasons and cannot be cleared using standard diagnostic tools, necessitating professional repair.

Over time, internal electronic components may fail, leading to persistent fault codes indicating a defect within the control unit itself. These errors cannot be resolved simply by clearing the fault memory.

Another well-known issue involves physical damage to the connector or circuit board. Corrosion caused by moisture ingress or damaged pins on the CAN‑bus connector can lead to intermittent or permanent communication failures with other control units in the vehicle.

Water damage or short circuits resulting from external factors can also destroy the complex internal electronics, causing total failure of the airbag system.

How do you recognize a fault in 39790-SZ3-003?

A malfunction of control unit 39790-SZ3-003 typically manifests unmistakably through a permanently illuminated or flashing airbag warning light on the instrument cluster. Additionally, the control unit may become inaccessible to diagnostic equipment, making fault analysis impossible.

The clearest indicator is the airbag warning light, which fails to extinguish after starting the vehicle, signaling that the safety system is not operational and would not activate in the event of a crash.

During workshop diagnostics, fault codes are often read out, directly pointing to an internal defect in the control unit—codes that usually cannot be permanently erased.

In some cases, the control unit is completely “dead,” no longer responding to requests from diagnostic tools. This complete loss of communication prevents further troubleshooting of sensors or other components of the airbag system.

In which vehicles is control unit 39790-SZ3-003 installed?

The OEM part number 39790-SZ3-003 is specific to Honda vehicles. It is primarily used in the first generation of the Honda Legend, manufactured between 1985 and 1990. Occasionally, it has also been identified in later models, such as the 1999 Honda Legend equipped with a 3.5-liter engine.

At Airbag24, the airbag control unit with part number 39790-SZ3-003 is refurbished for the following specific models:

Honda: First-generation Legend (vehicles built between 1985 and 1990).

Honda: Legend (specific vehicles from the 1999 model year equipped with a 3.5-liter gasoline engine).

As an original manufacturer component, full compatibility and functionality are fully restored after professional repair.

How does the repair of 39790-SZ3-003 proceed at Airbag24?

Following removal and shipment of the defective control unit to Airbag24, a detailed incoming inspection is performed. Subsequently, crash data is professionally erased, hardware defects are repaired at the component level, and faulty parts are replaced. A comprehensive final test ensures full operational capability, backed by 2 years' statutory liability for defects.

The process begins with the proper removal of the control unit from the vehicle, ideally carried out in a specialized workshop to avoid damage.

Upon receipt at Airbag24, the unit undergoes meticulous analysis to verify the reported cause of failure. Communication is checked, and the fault memory is read out.

The actual repair takes place on the circuit board. Technicians erase stored crash data, fix cold solder joints, repair conductive traces, and replace defective electronic components. Only what is truly faulty is repaired.

Finally, the refurbished control unit is tested on a test bench to ensure proper functionality of all systems and stable communication. We provide 2 years' statutory liability for defects on the completed repair.