What does it mean?
B1793 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Occupant Classification Sensor Power Supply Circuit Malfunction .
Symptoms
- Airbag warning lamp on and the occupant classification system out of service
- Passenger airbag on or off indicator stuck, or the airbag simply switched off
- All sensor readings missing or reading zero at the same time on the scan tool
- Several occupant classification codes set together rather than a single sensor code
- Fault can come and go as the seat is slid forward and back
Likely causes
- Open or high-resistance supply wire between the module and the sensors, often under the seat
- Under-seat connector corroded or wet after carpet cleaning, a spill or a leaking seal
- Supply wire shorted to ground somewhere in the seat loom, pulling the rail down
- Harness pinched by the seat rail as the seat is moved, breaking or grounding the feed
- Blown fuse or poor ground point for the occupant classification module
- Weak battery or unstable charging keeping system voltage too low
- Occupant classification module with a failed internal voltage regulator
How to fix it
- Read all occupant classification codes; a whole group of them points at the supply rather than one sensor
- Test the battery and charging system voltage before anything else
- Check the fuse and the module ground point, cleaning any corrosion found
- Measure supply and ground voltage at the module and at a sensor connector with the ignition on
- Wiggle-test the seat loom through the full travel while monitoring supply voltage for dropouts
- If the rail is pulled low, disconnect sensors one at a time to find the branch causing the short
- Repair the harness or connector; replace the module last and carry out the required calibration afterwards