What does it mean?
B1796 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Sleep Operation Failure Of Occupant Classification ECU .
Symptoms
- Battery goes flat after the car sits a day or two
- Slow cranking or no start after an overnight park
- Airbag warning lamp on with the classification code stored
- Parasitic current draw measured well above specification
- Module still responds to a scan tool long after the key is removed
Likely causes
- A wake-up input stays active, most often a door, hood or trunk ajar switch stuck closed
- Body network keeps running because another module refuses to sleep and keeps the bus awake
- Ignition or accessory sense wire to the module stuck at voltage with the key off
- Internal failure of the module sleep control circuit
- Moisture in the under-seat connector creating a leakage path that mimics an active input
- Aftermarket electronics spliced into the body harness holding circuits alive
- Outdated module software with a known sleep timing issue
How to fix it
- Measure parasitic current after the normal sleep timer has expired, without opening a door
- Check every ajar switch (doors, hood, trunk) in live data with everything closed
- Watch bus activity after the key is off to see which module keeps talking
- Pull fuses one at a time while monitoring the current to isolate the circuit
- Disconnect the occupant classification module and confirm the draw drops
- Measure the ignition or accessory sense wire at the module with the key off
- Update the module software if an update exists, otherwise replace and calibrate the module