What does it mean?
B1804 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Driver Door Lock/Unlock Switch Circuit Stuck Unlock .
Symptoms
- Doors will not stay locked, or unlock by themselves after locking
- Alarm cannot be armed, or disarms shortly after arming
- Repeated actuator noise from the doors while parked
- Security risk because the vehicle unlocks unattended
- Battery drain from constant actuator activity
Likely causes
- Unlock contact stuck closed inside the switch pack
- Corrosion or moisture bridging the unlock contact
- Unlock signal wire shorted to ground and permanently active
- Damaged harness in the hinge boot where two conductors touch
- Trim or armrest fouling the switch after reassembly
- Aftermarket central locking module driving the unlock line continuously
- Door module input latched in the active state
How to fix it
- Watch the unlock switch status in live data with nothing pressed
- Unplug the driver switch pack and see whether the status returns to inactive
- Measure the unlock contact resistance at rest, it should be open
- Inspect the door for water intrusion and check the drain holes
- With the module unplugged, ohm the unlock wire to ground to find the short
- Disconnect any aftermarket locking module and retest
- Replace the switch pack or repair the harness before considering module replacement