What does it mean?
B1803 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Driver Door Lock/Unlock Switch Circuit Stuck Lock .
Symptoms
- Doors relock by themselves right after being unlocked
- Lock actuators click repeatedly or buzz continuously
- Risk of being locked out because the unlock command is overridden
- Battery drain from actuators being commanded over and over
- Alarm arms unexpectedly while the driver is still nearby
Likely causes
- Lock contact mechanically stuck closed by wear, debris or a broken return spring
- Water and corrosion bridging the lock contact inside the switch pack
- Signal wire permanently shorted to ground so the module reads a constant lock command
- Another switch sharing the same lock circuit shorted and holding the line active
- Trim panel or armrest pressing on the switch after a poor reassembly
- Module input stuck in the active state internally
How to fix it
- Read the switch status in live data with the switch untouched
- Unplug the driver switch pack; if the status clears, the switch is the fault
- Remove the door trim and check for water in the switch and around the module
- Measure the resistance of the lock contact at rest, it must read open
- If the state stays active with the switch unplugged, disconnect the other switches on the shared circuit
- Ohm the signal wire to ground with both ends free to find the short
- Replace the switch pack or repair the harness, and only then consider the door module