B1402 airbag control unit fault

What does error code B1402 indicate in the airbag control unit?

Error code B1402 signifies a specific grounding fault (Grounding Error) in the driver’s airbag circuit, also known as the squib circuit. The airbag control unit detects a ground short or an improper connection, can no longer reliably monitor the airbag’s status, and deactivates it for safety reasons, causing the airbag warning light to illuminate.

Technically, the control unit continuously monitors the resistance of the ignition circuit for the driver’s airbag. A grounding fault—i.e., an unintended connection to the vehicle’s chassis—causes this resistance value to fall outside the specified tolerance range.

The system interprets this condition as a critical malfunction, as proper deployment in the event of a crash can no longer be guaranteed. To prevent false activation, the affected airbag channel is disabled, and error code B1402 is permanently stored in the fault memory.

Typical symptoms of error code B1402

The most noticeable symptom of error code B1402 is the persistently illuminated airbag warning light (SRS light) on the instrument panel. This indicates a serious malfunction that results in immediate deactivation of the driver’s airbag. In the event of a crash, this airbag will not deploy.

The warning light does not extinguish after starting the engine as usual but remains constantly lit, signaling that the fault is permanent rather than intermittent.

When reading the fault memory with an appropriate diagnostic tool, error code B1402 appears alongside descriptions such as “Driver Airbag Squib Ground Short” or “Driver Airbag Squib Circuit Ground Short.” Other vehicle functions are typically unaffected.

The most common causes of error code B1402

The cause of B1402 is almost always a hardware defect in the driver’s airbag ignition circuit. First among these is a faulty steering wheel coil spring (slip ring), followed by an internal defect in the airbag squib, corroded ground connections, or a broken wire. Less frequently, the fault originates directly within the airbag control unit itself.

The most frequent source of failure is the steering wheel coil spring, also called the slip ring or steering wheel spiral. This component provides the electrical connection to the airbag while the steering wheel turns. Due to constant movement, the delicate conductive traces inside may break or rub against each other, leading to a ground short.

The driver’s airbag squib—the actual triggering element within the airbag module—can also develop an internal short to ground. Similarly, poor or corroded ground points in the airbag system, or mechanical damage to the wiring harness connecting to the steering wheel, can trigger the fault.

In some cases, the root cause lies directly on the airbag control unit’s circuit board, where a component in the driver’s airbag monitoring circuit has failed. Therefore, before repairing the control unit, external components must be carefully inspected.

In which vehicles does error code B1402 occur most frequently?

Error code B1402 primarily affects a wide range of Mitsubishi models, from compact cars like the Colt to SUVs such as the Pajero and the L200 pickup. Specific Kia models, including the Sorento, and Alfa Romeo models, such as the Giulia series, are also commonly affected.

At Airbag24, we repair airbag control units exhibiting error code B1402 for the following models and series:

Alfa Romeo: Giulia 952 (2016–2023) and 952 Facelift (2023–present).

Kia: Sorento XM (2009–2014).

Mitsubishi passenger cars: Mirage (CA, CC, CK, LA), Colt (CC, CJ, CZ), Space Star (A00), Lancer (CB, CH, CZ) and Lancer Evolution (I, II, V, VI, IX, X), Carisma (DA1A, DA2A), Galant (E50, EA, VR-4), Eclipse (D20, D30, D40), Eclipse Cross (GK), 3000GT (Z10) and GTO (Z10).

Mitsubishi SUVs & vans: Space Wagon (N30), Chariot (N40, N80), Grandis (NA), ASX (GA), RVR (N10, N20, N60, N70, GA), Outlander (GF), Outlander Sport (GA), Outlander PHEV (GG), Pajero (V40, V60, V70), Montero (V20, V60, V70, V80) and Shogun (V20, V70).

Mitsubishi pickups & commercial vehicles: Pajero Sport (K90, KS, QE), Montero Sport (K90), L200 (K60, K74, KA, KB, KJ), Triton (K60, K74, KB, KK), Strada (K60, K70, KB, KJ, KK), Delica (P20, P30, CV, D:5), eK Wagon (B11W), eK Custom (B11W), eK Space (B11A), Toppo (H80A), Town Box (DS17W), Attrage (A10) and Xpander Cross (A05A).

Procedure for repairing error code B1402

Professional repair of error code B1402 focuses on eliminating the grounding fault directly within the airbag control unit. Following an initial inspection, the electronics on the circuit board are analyzed, the fault in the driver’s airbag circuit is corrected, and the fault memory is cleared. After a final check, the refurbished unit is returned ready for installation, complete with 2 years’ statutory liability for defects.

Repair at Airbag24 follows a proven and reliable process. First, the local workshop should confirm that the coil spring and wiring are not the cause. The airbag control unit is then removed and shipped to us.

Upon receipt of the control unit, our technicians perform a thorough analysis to pinpoint the internal ground fault on the circuit board. Using specialized tools, the fault in the driver‑airbag deployment circuit is professionally repaired.

A crucial step is completely erasing the fault memory. This removes not only code B1402 but also any stored crash data that would otherwise prevent further use of the control unit.

Finally, the control unit undergoes rigorous quality and functional testing. This repair is an economically sensible and sustainable solution, as new parts are often very expensive or no longer available. We offer 2 years' statutory liability for defects on all repairs.