12-4X: Passenger Airbag Second Inflator Open

Circuit fault

What 12-4X means

Front passenger airbags on these cars use two inflator stages, and each stage gets its own monitored loop. The module sends a test current through the stage two pair and compares the resistance to a fixed window. A reading above the window, or no continuity at all, produces 12-4X and shuts the passenger side of the system down.

The path here is shorter and less exciting than the driver side, since nothing rotates. It runs from the SRS unit, through the harness behind the dash, to the connector at the airbag module above or behind the glovebox, and into the inflator. Most failures happen at the connector, because that is the part people disturb during unrelated dash work.

Common causes

• The airbag connector left partly seated after glovebox, HVAC, or radio work
• Terminals spread or pushed back in the connector body from repeated unplugging
• Harness damage behind the dash from a previous repair or an accessory install
• An inflator winding that has failed open inside the passenger airbag assembly
• Corrosion at the connector after water came in through the cowl or a leaking windshield

Crash data or hardware fault?

12-4X is a live resistance fault, which means the module is telling you what it reads right now. Restore the circuit and the code stops being current on the next self test. Crash data sits in a different category. It is written permanently when the bags fire and stays in the module until it is reset on the bench.

Does our reset clear it?

Clearing 12-4X on a scan tool leaves the open circuit exactly where it was, and the module stores the code again within seconds. Fix the connector, harness, or airbag first. A mail-in reset is the right service when the module is holding a locked deployment record, which is a separate condition from this resistance reading.

Which makes throw it

Our Acura lookup carries 12-4X for the passenger stage two circuit. Confirm the code against the index that matches the car in front of you before you commit to a test plan.

What to do next

Open the glovebox area and unplug the passenger airbag connector, then look closely at both halves for a terminal that has backed out or a latch that never clicked. Measure the inflator loop at the bag side to see whether the airbag itself reads open. If the bag reads open, you need a genuine OEM passenger airbag, and we pull and test Acura passenger assemblies here in Jacksonville. Related codes: 11-BX, 12-6X, B0073.