B1876 names the seat cushion airbag on the passenger side, an inflator built into the seat bottom on certain Lexus models. The module has found that firing circuit open and taken the system out of service.
A seat cushion airbag inflates inside the seat bottom to keep the occupant from sliding forward under the lap belt during a frontal impact. It fires through its own squib, and the airbag module monitors that squib circuit the same way it monitors the dash and door bags. B1876 is set when the measured loop reads open instead of the expected low resistance.
This circuit has a weak point most others do not. The harness has to cross from the floor into a seat that slides, reclines, and sometimes swivels, which means a flexing section of wire and at least one connector under the seat. Seat travel over years of use is a routine way for that circuit to open up.
Since the module reads this loop live, B1876 sits in the circuit family and rises or falls with the actual continuity of the wiring. A stored crash record is a different animal: the module writes it at deployment, keeps it permanently, and no amount of code clearing at the vehicle will remove it without a module reset.
Do not expect a reset to resolve this one. An open squib circuit is a physical condition on the vehicle, and clearing memory leaves the condition untouched. Repair the connector, the flex loop, or the inflator, then verify the code stays gone. Where our mail in reset earns its place is on modules that fired and are now locked with crash data after the repairs are complete.
This is a Lexus code, and the seat cushion airbag it refers to is a Lexus feature rather than something fitted across the wider Toyota line. If a vehicle stores B1876, it has that cushion inflator in the passenger seat bottom.
Run the passenger seat fully forward and fully back while watching the code, because a flex loop that only opens at one end of the travel gives itself away quickly. Then unplug and inspect the under seat connector for corrosion, spread terminals, and a latch that never engaged. Measure the squib loop at the seat connector to decide whether the fault is upstream in the floor harness or inside the seat, and call 501-988-0611 if you need a genuine OEM seat airbag assembly. Related codes: B1866, B1906, B1352.
Trace the wiring and connectors first. If the module still holds the fault after the repair, mail it to us and we will clear it.
Genuine OEM, tested, and shipped ground from Jacksonville, Arkansas.
Do not see it listed? Request a part or call 501-988-0611.