Airbag control unit with part number 6545HJ

What is the function of the airbag control unit 6545HJ?

The airbag control unit with part number 6545HJ is the central control unit (SRS ECU) for the passive safety system in the Peugeot 307 SW I. It processes signals from crash and acceleration sensors and, within milliseconds, decides whether to deploy airbags and seatbelt pretensioners to provide optimal protection for occupants in the event of a collision.

Technically, the 6545HJ serves as the brain of the Supplemental Restraint System (SRS). It continuously monitors all connected components, including front, side, and head airbags, seatbelt pretensioners, seatbelt buckle sensors, and seat occupancy detection.

Under normal operating conditions, the control unit performs continuous self-diagnosis. Any detected faults—whether in sensors, wiring, or the unit itself—are indicated by the airbag warning light on the instrument panel and logged as diagnostic trouble codes (DTCs) in the internal memory.

Following a crash, the unit stores event‑related and crash‑relevant data. This information often locks the control unit out of further use, making professional repair or replacement essential, as the safety function can no longer be guaranteed.

Why does the 6545HJ airbag control unit fail?

The most common cause of failure for the 6545HJ control unit is the storage of crash data after an accident, which triggers an electronic lockout. Other defects include internal electronic malfunctions that result in non‑erasable fault codes, communication issues via the CAN bus, or physical damage caused by water ingress.

After a collision in which airbags or seatbelt pretensioners have deployed, a so‑called “crash record” is stored in the control unit’s memory. This record prevents reactivation and must be professionally cleared to restore full functionality.

A frequent issue is internal electronic malfunctions, often signaled by error codes such as “control unit defective” or “internal error,” which cannot be erased even with a diagnostic tool. These are typically due to faulty memory chips, driver ICs, or problems with the power supply on the circuit board.

Communication with the vehicle may also break down, rendering the control unit unreachable via the OBD interface. This can stem from defective CAN‑bus drivers inside the unit or corrosion at the connector pins, caused by moisture in the vehicle interior—especially in the footwell area.

Rarely, external factors like reverse polarity during jump-starting can lead to short circuits, damaging protective diodes or voltage regulators within the 6545HJ. Such damage is usually repairable.

How do you recognize a defective 6545HJ control unit?

A defect in the 6545HJ control unit primarily manifests as a permanently illuminated or flashing airbag warning light on the dashboard. Additionally, specific fault codes indicating an internal malfunction cannot be cleared. In some cases, the control unit becomes completely inaccessible to diagnostic tools.

The clearest sign is the active airbag warning light. If it remains lit after starting the engine, the system indicates a critical fault that compromises the operation of airbags and seatbelt pretensioners.

During workshop diagnostics, fault codes are read. Typical entries for a defect in the 6545HJ itself include “internal error,” “control unit defective,” or errors suggesting a failed self‑diagnostic test—none of which can be permanently resolved.

Another clear symptom is complete loss of communication. When the workshop attempts to access the airbag control unit via the OBD port, the connection fails—the unit no longer responds to diagnostic requests.

In which vehicles is the 6545HJ control unit installed?

The 6545HJ airbag control unit is an original Peugeot component specifically designed for the first‑generation Peugeot 307 SW. At Airbag24, we repair this control unit for both pre‑facelift and facelift models of this series. It is often listed alongside the related variant 6545HF.

The repairs offered by Airbag24 cover the following specific models where the 6545HJ or its closely related variant 6545HF is used:

Peugeot 307 SW I (model years 2001–2005)

Peugeot 307 SW I Facelift (model years 2005–2009)

How is the 6545HJ professionally repaired?

Professional repair of the 6545HJ at Airbag24 includes precise fault diagnosis on a specialized test bench, elimination of the root cause—such as clearing crash data or replacing defective components—and a final functional check. We provide 2 years' statutory liability for defects on every repair.

After you send the removed control unit to Airbag24, an initial incoming inspection is performed. During this process, all stored fault codes and any available crash data are read out to precisely identify the defect.

If the failure is due to a collision, the crash data is professionally erased from the internal memory. This restores the control unit to its pre‑accident condition, making it fully functional again—provided that all deployed airbags and seatbelt pretensioners have been replaced in the vehicle.

In cases of electronic faults, the defective components on the circuit board are identified and replaced. These may include voltage regulators, memory chips, or driver ICs. Damage caused by corrosion or cold solder joints is also repaired during the restoration process.

Finally, a comprehensive functional test is carried out. Communication is checked, and it is confirmed that no internal errors remain. Only after this successful test is the repaired control unit approved for return shipment.