B1906: Left Front Pretensioner Squib

Circuit fault

What B1906 means

P/T squib LH is the manufacturer shorthand for the left hand pretensioner igniter. That igniter lives inside the seat belt retractor at the B pillar or inside the buckle assembly, depending on the model. The airbag module pushes a test current through it and watches the resistance. B1906 is stored when that current finds an open path instead of the winding it expects.

Pretensioner circuits fail differently than dash mounted airbag circuits. The wiring has to reach a retractor buried in the pillar or a buckle that moves with the seat, and the connectors sit where trim panels come off and go back on. A pretensioner also fires once and is done, so a retractor from a previously wrecked vehicle will read open from the moment it is installed.

Common causes

• A pretensioner that already fired in an earlier crash and was never replaced
• The yellow connector at the retractor or buckle left unlatched after B pillar trim work
• Harness damage where the wiring passes through the seat rail or under the sill plate
• An open igniter winding inside an otherwise undamaged retractor
• Corroded terminals from water entering at the door seal or rocker area
• A module connector not fully locked after a previous airbag repair

Crash data or hardware fault?

B1906 measures a live circuit, so it belongs with the circuit codes and it comes and goes with the condition of the loop. That is the practical difference from crash data, which is written into memory at the moment of deployment and stays there permanently regardless of what the wiring does afterward.

Does our reset clear it?

The mail in reset does not restore an open pretensioner loop. If the pretensioner already fired, the retractor or buckle assembly has to be replaced before anything electrical will read correctly. Once the hardware is in and the wiring is verified, a module that is also holding crash data from that same event is exactly what we clear. Order the repairs that way and the job holds.

Which makes throw it

Both Lexus and Toyota use B1906 with the same definition for the left front pretensioner. Which side that is depends on nothing more than where the steering wheel sits, and on these vehicles the left front is the driver position.

What to do next

Determine first whether the pretensioner has already deployed, since a fired unit reads open and no amount of wiring work will change that. Look for a shortened, locked belt and a discolored retractor. If the unit is intact, unplug and reseat the yellow connector at the retractor, then measure the loop at both ends to isolate the break. We stock genuine OEM seat belts and pretensioners and can rebuild a fired retractor for many Toyota and Lexus applications. Related codes: B1876, B1926, B1034.