B1608 airbag control unit fault

What does error code B1608 mean in the airbag control unit?

Error code B1608 indicates a specific electrical interruption in the ignition circuit of the driver’s seatbelt pretensioner. The control unit detects an “open circuit,” meaning the resistance in the circuit is infinitely high. This is classified as a critical system fault that disables the protective function of the seatbelt pretensioner in the event of a crash.

Technically, the control unit cannot send current to the pyrotechnic charge of the seatbelt pretensioner because the electrical connection has been broken. The system registers this condition as a permanent fault, which typically cannot be easily cleared and triggers the airbag warning light.

This fault often causes the control unit to enter a locked state. It may refuse communication with external diagnostic tools, making troubleshooting difficult and potentially leading to a false diagnosis of a completely defective control unit.

How can you recognize error code B1608?

The main symptom of error code B1608 is a permanently illuminated airbag warning light on the instrument panel. In some cases, the light stays on for about 30 seconds after turning on the ignition before remaining lit continuously. Additionally, communication with the airbag control unit via an OBD diagnostic tool is often no longer possible.

Another clear indication is that error code B1608 cannot be erased from the fault memory. Even if the external wiring is inspected and found to be intact, the fault remains stored in the control unit, suggesting an internal defect or saved crash data.

Especially after a collision—even if no airbags deployed—the control unit may lock up and display error code B1608. For safety reasons, the system is then disabled and requires professional repair.

What causes error code B1608?

The most common cause of B1608 is a physical break in the electrical circuit of the driver’s seatbelt pretensioner. This can result from damaged cables, corroded or loose connectors. If the external wiring is intact, the fault usually lies internally within the airbag control unit itself, often due to an accident or material fatigue.

An additional significant cause is the storage of crash data in the control unit following an impact. Even without deployment of airbags or seatbelt pretensioners, the event is logged in memory, locking the system. Error code B1608 can directly result from this lockout.

In the context of the Mitsubishi ASX GA, error code B1608 frequently occurs alongside related codes. These include code B1C47, which points to an identical issue in the passenger-side seatbelt pretensioner circuit, as well as error code B1557, also indicating a malfunction in the seatbelt pretensioning system.

On which vehicles does error code B1608 appear?

Error code B1608 is specific and is primarily associated with the Mitsubishi ASX vehicle platform in diagnostic logs. While similar fault patterns exist across other manufacturers, this particular identifier is typical for this model series.

At Airbag24, this error code is recognized as a known issue for the following model and its corresponding production series:

Mitsubishi ASX (GA series, from model year 2010 onward)

How is error code B1608 repaired?

Professional repair focuses on electronic refurbishment of the original airbag control unit. Rather than replacing it with an expensive new part, the hardware is analyzed at the component level, the fault in the seatbelt pretensioner circuit is fixed, and any existing crash data is completely erased. The repaired unit is then fully functional again.

The process begins with the proper removal of the control unit from the vehicle after disconnecting the battery. In the Mitsubishi ASX GA, the unit is typically located in the rear compartment beneath a cover. The removed module is then sent in for repair.

Upon receipt by Airbag24, a detailed diagnosis of the circuit board is performed. Technicians check the ignition circuits for breaks and repair affected traces or components. A crucial step is resetting the internal memory to factory settings, ensuring all faults and crash data are completely cleared.

Following successful repair and a final functionality test, the control unit becomes a “plug-and-play” solution once more. No re-coding or re-learning is required in the vehicle. All repairs come with 2 years' statutory liability for defects.