B1816: Passenger Airbag Squib, Second Stage

Circuit fault

What B1816 means

A dual stage passenger airbag has two igniters inside the same inflator. The module chooses how many to fire based on crash severity and what the occupant sensing tells it. B1816 means the circuit to the second igniter does not read continuous, so the module cannot count on that stage being available and shuts the whole system down.

The circuit runs from the module, through the dash harness, into the yellow connector at the airbag, and through the squib winding itself. An open anywhere on that path sets the same code. Stage one can read perfectly normal while stage two is open, which is why the code calls out the second step specifically.

Common causes

• A yellow SRS connector at the passenger airbag not fully latched after glovebox or dash work
• A broken or stretched conductor in the dash harness behind the glovebox
• An inflator squib that has failed open internally
• Terminal damage or a spread pin at the airbag control module connector
• A shorting bar in the connector that did not release when the plug was seated
• Corrosion at the connector from water coming in at the cowl or windshield

Crash data or hardware fault?

Continuity here is measured live, which puts B1816 in the circuit family. The module measures the loop repeatedly and the code follows what the wiring actually does. That behavior separates it from crash data, which is a permanent record of a deployment that stays in the module no matter how many times a scan tool clears codes.

Does our reset clear it?

A module reset will not put continuity back in an open squib circuit. The fault has to be found and repaired on the vehicle, and the code will return on the next self test otherwise. Where the reset does apply is after a crash, when the module is carrying deployment data alongside the circuit complaint. Repair the circuit, replace what deployed, then send us the module.

Which makes throw it

Lexus and Toyota both list B1816 for the front passenger second stage squib. It only appears on vehicles fitted with a dual stage passenger airbag, so its presence confirms the chassis has staged deployment.

What to do next

Unlatch and reseat the yellow connector at the passenger airbag before anything else, because an incomplete latch leaves the shorting bar engaged or the pins short of contact and mimics an open perfectly. Then measure resistance across the stage two loop at the module connector to split the fault between the harness and the airbag. If the inflator reads open, the airbag assembly is what needs replacing, and we stock genuine OEM passenger airbags for Toyota and Lexus. Related codes: B1811, B1826, B0019.