B1404 airbag control unit fault

What does error code B1404 mean?

Error code B1404 indicates a general, internal problem in the airbag control unit. It is stored as a validated fault and usually points to a hardware defect or a serious communication failure. As a result, the airbag warning light remains illuminated permanently, and the system’s protective function is no longer guaranteed.

Technically speaking, code B1404 signifies that the airbag control unit (ECU) has detected an irreparable internal fault during a vehicle cycle. This fault has been validated, meaning it is persistent rather than intermittent.

The control unit then switches to a safety mode to prevent unintended airbag deployment. This inevitably deactivates the entire restraint system, making prompt diagnosis and repair critical for safety.

How can you recognize error code B1404?

The primary and unmistakable symptom of error code B1404 is the continuously illuminated airbag warning light on the instrument panel. This light does not turn off after starting the vehicle. In some cases, communication issues with the control unit may also occur during diagnostics, complicating fault analysis.

The airbag warning light (often referred to as the SRS light) directly alerts the driver to a critical issue within the safety system. In this state, the system is non-functional and offers no protection in the event of a crash.

When attempting to read the fault memory using universal diagnostic tools, the control unit may fail to respond. For accurate diagnosis—especially in Mitsubishi models—a manufacturer-specific system such as the MUT-II is often required.

What causes B1404?

The main cause of error code B1404 is typically an internal defect within the airbag control unit itself, such as faulty electronic components or cold solder joints. Other common reasons include peripheral issues like loose connections at connectors under the seats, malfunctions in seatbelt pretensioners, or stored crash data following an accident.

A frequent trigger is hardware or software problems directly within the control unit. These range from defective microcontrollers and damaged circuit traces to errors in memory chips. Electrical damage caused by overvoltage or water ingress can also lead to such internal defects.

Another classic source of trouble is poor connector contacts or damaged cables. In particular, the connectors beneath the front seats—leading to the seatbelt pretensioners and side airbags—are prone to loose connections due to seat adjustments.

Problems with the seatbelt pretensioners themselves or their sensors can also trigger error code B1404. Sometimes, a trial replacement of components is necessary to pinpoint the exact source of the fault in the peripheral system.

Following a crash, so‑called crash data is stored in the control unit’s memory. This data blocks the unit’s functionality and must be professionally erased before the system can return to operational status. Simply clearing the error code is insufficient in these cases.

Which vehicles are affected by B1404?

Error code B1404 occurs frequently in various Mitsubishi models, including the Space Star, Lancer, and Outlander. However, it can also appear in European manufacturers such as Renault’s Twingo RS II or Škoda’s Karoq. At Airbag24, we professionally resolve this fault across a wide range of affected vehicles.

With over 20 years of experience repairing airbag control units, Airbag24 has developed extensive expertise in handling error code B1404 for the following brands and models:

Mitsubishi: Affected models include the Mirage (CM), Space Star (DG, DG Facelift), Lancer (CJ), Eclipse (D50), Chariot (N30), Outlander (PHEV ZL), Pajero (V80, V80 Facelift), Challenger (K90), Strada (K74), and Dingo (CQ).

Renault: This error code is particularly well-known in the sporty Twingo RS II.

Škoda: The fault also appears in the Karoq, both in the first-generation model (2017–2021) and in the facelifted version (from 2021 onward).

How is professional B1404 repair performed?

Professional repair of error code B1404 begins with precise diagnostics to rule out external causes. After sending the removed control unit to Airbag24, a component-level analysis is conducted. Defective parts are replaced, circuit traces repaired, cold solder joints fixed, and any stored crash data erased.

Before removing the control unit, a visual inspection of all relevant components—such as connectors and cables—should be carried out to exclude peripheral causes. Following removal, the control unit is sent in for restoration.

At Airbag24, repairs follow a proven process: First, the unit is scanned with specialized equipment to precisely pinpoint the internal fault. Then, technicians open the control module and perform an electronic inspection at the component level.

The actual repair, depending on the nature of the damage, may involve fixing circuit traces, resoldering cold solder joints, or replacing defective electronic components. If present, any stored crash data is permanently erased from memory.

Following successful repair, the fault memory is cleared using the appropriate diagnostic software, and the unit undergoes a final test. We provide a 12-month warranty on every repair.