Airbag control unit with part number 685104EH4A

What is the function of the airbag control unit 685104EH4A?

The airbag control unit with part number 685104EH4A is the central control unit (SRS ECU) of the occupant protection system in the Nissan Qashqai J11. It continuously analyzes data from acceleration and yaw rate sensors to deploy airbags and seatbelt pretensioners with millisecond precision in the event of a crash, thereby protecting occupants.

This component serves as the brain of the passive safety system. It communicates with all relevant sensors, including front, side, and pressure sensors. When a collision exceeding a defined threshold is detected, the ECU sends ignition signals to the respective pyrotechnic charges in the airbags and seatbelt pretensioners.

In addition, it stores relevant event data—known as crash data—in non-volatile memory. This ensures that after an incident, the system’s status and the severity of the accident can be analyzed. The unit also performs a self-test upon each engine start and indicates its operational readiness via the airbag warning light.

Why does the control unit 685104EH4A fail?

The most common reason for needing repair on the control unit 685104EH4A is the storage of crash data following a collision, which results in the unit being locked. Other causes include internal electronic defects, moisture damage, faulty wiring, or loose connectors that impair functionality.

After a collision—even a minor one—the control unit becomes locked by permanently storing crash data in its internal memory (often an EEPROM chip). This mechanism is a manufacturer‑imposed safety feature designed to prevent further use until a professional inspection and reset have been performed.

Besides crash‑related failures, age‑related defects in electronic components such as capacitors or processors are also frequent causes. Moisture entering through body panel leaks can lead to corrosion on the circuit board and cause short circuits.

It’s important to note that this control unit is also known under other part numbers considered equivalent and may exhibit the same defects. These include: 98820BK10A, 988204EH0C, 685204EH0A, 68520HV00A, 98820BK00A, and K88204EH0D.

How do you recognize a defect in the 685104EH4A?

A defect in the control unit 685104EH4A primarily manifests as a permanently illuminated or flashing airbag warning light on the instrument cluster. Often, the control unit can no longer be read by a diagnostic tool, or error codes remain stored that cannot be cleared, such as “crash data stored” or “side airbag error.”

The clearest indication is the activated SRS indicator light (Supplemental Restraint System). If this light stays on after starting the engine or begins to illuminate again shortly thereafter, it signals a system fault.

In many workshops, it is then found that communication with the control unit cannot be established. The unit fails to respond to diagnostic requests, making precise fault analysis difficult.

In other cases, while the fault memory can be read, the stored error codes—especially after an accident—are permanent and cannot be erased using standard diagnostic tools.

A secondary symptom may be the failure of steering wheel buttons. This is often due to a defective slip ring (winding spring), though diagnosing this requires removing the airbag and reading the fault memory. Before repairing the control unit, a specialized workshop should always check whether the issue lies instead in the wiring or external sensors.

In which vehicles is the control unit 685104EH4A installed?

The airbag control unit with part number 685104EH4A is an original Nissan replacement part specifically developed for the Nissan Qashqai model series. At Airbag24, we repair this control unit for the following specific models and production years of the J11 generation.

The compatibility of this control unit covers the entire second generation of the popular SUV model. Specifically, repairs are offered for the following vehicles:

Nissan Qashqai J11 (model years 2013–2017)

Nissan Qashqai J11 Facelift (model years 2017–2021)

Is it worth repairing the control unit 685104EH4A?

Yes, repair is highly cost‑effective. A new control unit often costs over 500 euros at Nissan, whereas a professional repair is significantly cheaper and restores full functionality. You not only save substantial expenses but also avoid potential compatibility issues or coding complications that can arise with used parts.

The biggest advantage is the significant cost savings compared to buying a new unit. Instead of purchasing an expensive new part, the existing original control unit is refurbished. This ensures that the vehicle’s original configuration remains intact.

A refurbished control unit is essentially “plug-and-play,” as it is already programmed for your specific vehicle. In contrast, used control units from donor vehicles often carry the risk of having stored crash data or a different configuration, requiring time-consuming reprogramming.

A professional repair—where crash data is erased and defective components are replaced—restores the control unit to full functionality and safety. Additionally, the repair comes with a 12-month warranty.

How does the repair process work at Airbag24?

The repair process at Airbag24 is simple and transparent. After professionally removing the faulty control unit, you send in part number 685104EH4A. Our technicians perform a precise diagnosis, reset the stored crash data, replace any defective electronic components, and restore full functionality—including a 12-month warranty.

The process ideally begins with a fault diagnosis at your workshop to confirm that the issue truly lies within the control unit. Following removal—typically under the passenger seat or in the center console with the battery disconnected—you securely package the unit and ship it to Airbag24.

Upon receipt, our specialists analyze the circuit board and memory of the control unit. The repair includes professionally erasing crash data using specialized programming equipment. If necessary, defective components such as capacitors, memory chips, or processors are desoldered and replaced with new, high-quality parts.

After refurbishment, the control unit undergoes a comprehensive functional test on a test bench to simulate proper communication and operation. It is then returned to you and can be reinstalled in your vehicle.

What shipping options does Airbag24 offer?

Airbag24 provides flexible and secure shipping options. You can either send your defective control unit yourself at no charge or conveniently arrange a UPS pickup from your preferred location. For return shipping, you have free standard UPS delivery, faster UPS Express delivery, and both options available with cash-on-delivery.

For sending your unit to us, you have two choices: either mail it directly to us yourself, or use our convenient UPS pickup service, which collects the package right from your workshop or home.

Once the repair is complete, you can select from the following return shipping options:

Free standard UPS delivery (1–3 business days).

Faster UPS Express delivery (1–2 business days) for exceptionally swift delivery.

Standard UPS delivery with cash-on-delivery (1–3 business days) if you prefer to pay upon receipt.

Express UPS delivery with cash-on-delivery (1–2 business days) for the fastest option with payment upon arrival.

In addition, upon prior arrangement, you may also choose to pick up the repaired control unit in person from our facility.