What does it mean?
B1311 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Door Lock-Link Switch Circuit (Unlock) Failure .
Symptoms
- Central locking does not unlock that door, or unlocks it only occasionally
- Remote key and keyless entry work on the other doors but not this one
- The alarm may trigger without reason, or the vehicle refuses to arm
- Interior lamps or the door status display behave incorrectly
- Unlocking from the inside handle is not registered by the system
Likely causes
- Worn or contaminated unlock contacts inside the door latch assembly
- Water running down inside the door onto the latch switch after the vapour barrier has been torn
- Broken or stretched wire in the door jamb loom that flexes each time the door opens
- Corroded door jamb connector
- Latch actuator worn so the internal switch is never fully triggered
- Short to ground on the unlock signal circuit
- Door module or body module input stage failure
How to fix it
- Watch the lock and unlock switch states in live data while operating the latch by hand
- Flex the door jamb loom inside its rubber boot and look for broken strands
- Remove the door trim, check for water intrusion and repair the vapour barrier
- Check the latch connector for corrosion and confirm it is fully seated
- Measure continuity of the unlock signal wire between the latch and the module
- Replace the door latch assembly when its internal switch does not change state reliably
- Repair the jamb harness, replace the door module last, then retest every locking function