B1155 is Toyota's code for a fault in the curtain shield airbag sensor assembly on the left side of the vehicle. The full Toyota number is B1155/39, and it only shows up on vehicles built with side and curtain airbags. It names a sensor and the wiring that feeds it, so it is hardware rather than a stored crash record.
The curtain shield airbag sensor assembly LH is a small satellite sensor mounted low on the left side of the body. Inside it are a lateral deceleration sensor, a safing sensor, and its own diagnostic circuit. It watches for a side hit, decides whether the impact is severe enough to matter, and reports to the center airbag sensor assembly, which is what Toyota calls the airbag control module. B1155/39 is stored when that left side sensor reports a fault or stops answering the module.
Two details help when you are searching this code. The number Toyota prints is five digits plus a subcode, so B1155 and 39 belong together, and the right side twin of this sensor is B1154/38. Also, on the Toyota charts that use these numbers, side and curtain faults make the SRS warning light blink rather than stay on steady. Owners often call in describing a flashing light as a different problem than a solid one.
Toyota lists three trouble areas for B1155: the curtain shield airbag sensor assembly LH, the left floor wire that runs to it, and the airbag sensor assembly. That is the whole search area.
Hardware. B1155 names a physical part and the wiring to it, and the module is only passing along what the left sensor told it. The diagnostic order is the connector, then the floor wire, then the sensor, then the module.
Cars that come out of a side collision often carry B1155 along with a locked crash record, because the same impact that fired the curtain bag can take out the sensor. Those are two separate repairs on the same vehicle.
Not on its own. A reset restores the module's memory, and B1155 is a live report about a sensor circuit, so it comes right back at the next key on while the fault is still there. Replace or repair the failing piece first.
If the vehicle was damaged and the module is also holding a deployment record, that part is our work. Once the sensor and any deployed curtain airbag are back in, our airbag module reset clears the stored crash data from your original module. If the sensor itself is what failed, genuine OEM side and impact sensors are searchable by vehicle in the parts store.
B1155/39 belongs to Toyota and Lexus, which share the same SRS chart and the same center airbag sensor assembly naming. It only appears on vehicles equipped with side and curtain airbags, which is why a base model from the same year will never show it. Everything above B0999 is manufacturer defined, so a B1155 read off another brand is a different system and none of this applies.
Start under the left front sill and seat area. Unplug and reseat the sensor connector, look for green or white corrosion on the pins, and follow the floor wire for pinch damage or a repair splice from earlier work. Compare what you find against the right side circuit, since B1154/38 is the same part on the other side.
If the car has been in a side impact, get the curtain bag, the sensor, and the belt hardware handled before anyone worries about the light. Related Toyota codes are B1156 for the front airbag sensor on the right, B1610 for that same sensor under Toyota's later numbering, and B1100 for the center airbag sensor assembly itself.
Related codes: B1156, B1610, B1100
Keep reading:
Code scope: Toyota, Lexus. The same number can mean something different on another manufacturer, so match the code to your make before you act on it.
A reset clears stored crash data. A replacement part fixes a hardware fault. We have read these codes since the nineties and will tell you which one you are looking at.
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