What does it mean?
B1787 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Occupant Classification Sensor Rear LH Collision Detection .
Symptoms
- Airbag warning lamp on and the occupant classification system disabled
- Passenger airbag status indicator locked and no longer responding to the occupant
- Code returns immediately after any attempt to clear it
- System will not accept the zeroing or calibration routine
- Rear left weight reading is stuck at an extreme value
Likely causes
- Real impact to the vehicle registered through the seat structure
- Heavy luggage dropped onto the rear of the cushion, or someone kneeling on the seat back
- Seat lifted or supported by the cushion during removal and refitting
- Rear left load cell or its bracket deformed and now reading beyond its range
- Damaged sensor wiring producing a voltage spike interpreted as an impact
- Seat rail bent or the frame twisted, so the rear left corner is mechanically overloaded
- Occupant classification module fault
How to fix it
- Read all related codes and review the stored event data and freeze frame
- Ask about recent impacts, seat removal, or heavy loads carried on that seat
- Unload the seat completely and check the frame, rails, brackets and sensor mounts for bending or cracks
- Inspect the rear left sensor lead and connector for crush damage, chafe and corrosion
- Attempt the specified zero or calibration procedure and note the result
- If the event stays latched, replace the affected sensor or seat frame assembly following the manufacturer's instructions
- Recalibrate the system and confirm correct classification with the seat empty and with a known load