What does it mean?
B1331 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Decklid Ajar Rear Door Circuit Failure .
Symptoms
- Boot or tailgate ajar warning stays on permanently, or never appears at all
- Boot lamp stays lit and drains the battery
- The alarm will not arm, or is triggered by the rear door
- Remote release or the power tailgate may stop operating
- Interior lamp timing behaves incorrectly
Likely causes
- Faulty tailgate or boot lid latch switch, moisture reaches these easily
- Broken wire in the loom running through the tailgate hinge or the boot lid gooseneck
- Corroded connector at the latch or inside the tailgate
- Latch out of adjustment, so the lid never registers as fully closed
- Wiring damaged when fitting a reversing camera, spoiler or interior trim
- Water entering the tailgate past a failed seal
- Body control module input failure
How to fix it
- Monitor the boot lid / rear door input in live data while opening and closing the lid
- Flex the harness at the hinge or gooseneck while watching for signal dropouts
- Remove the trim and inspect for broken strands inside the rubber conduit
- Check the latch connector for corrosion and water, then dry and reseal it
- Test the latch switch continuity directly at its connector while operating the latch by hand
- Adjust or replace the latch when the switch does not change state reliably
- Repair the flexing harness with proper stranded wire and sealed joints, then retest the alarm and lighting