B1780 on Lexus: How to Diagnose & Fix
B1780 — Lexus-specific definition
1 Lexus model · 1 documented issue · 1 critical
B1780 on Lexus by model: symptoms, diagnosis and fix
Multiple 2022-2024 Lexus LX owners reported persistent SRS/airbag warning messages and dealer diagnoses related to the front passenger occupant classification system and related airbag components. These model years are covered by NHTSA recall 26V180 (Lexus 26LA03/26LB03): on LX models built July 30, 2021 through July 18, 2024, the front passenger seat may have insufficient clearance between the seat frame and a stopper, which can make the Occupant Classification System sensor misdetect the occupant, so the passenger airbag may not deploy correctly in a crash. Because the issue directly affects restraint-system operation, it is considered high severity even when the repair itself is covered by recall or warranty.
Common Symptoms
- SRS warning light illuminated
- Airbag system malfunction message
- Passenger airbag OFF/ON status behaving abnormally
- Warning appears after moving front passenger seat
- Repeated dealer visits for airbag-related faults
How to Fix
Scan the SRS system with a Toyota/Lexus-capable diagnostic tool and check recall 26V180 (Lexus 26LA03) status by VIN. Under the recall, dealers inspect the front passenger seat and replace the seat frame assembly as necessary at no charge, then clear codes and verify the occupant detection status with a seat calibration procedure. If the warning returns, wiring under the seat and connector tension should be checked carefully.
Sources for this issue (2)
B1780 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B1780 mean on a Lexus?
On Lexus, B1780: On Lexus/Toyota, B1780 is 'Front Occupant Classification Sensor LH Circuit Malfunction'. The occupant classification ECU sets it when it sees a line short, an open, a short to ground or a short to B+ in the front occupant classification sensor LH circuit for 2 seconds. The trouble areas are the No. 1 seat wire, the front seat assembly (the sensor) and the occupant classification ECU (Lexus/Toyota repair manual excerpts, e.g. manuals.autorepairshq.com Lexus CT 200h / ES 330 B1780). On Lexus it is documented across 1 model: LX.
How much does it cost to fix B1780 on a Lexus?
Repair costs vary widely with the root cause and Lexus model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.