What does it mean?
B1843 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Sunroof Close Switch Circuit/Performance .
Symptoms
- Sunroof will not close, or closes and then reopens by itself
- Express close function lost, the button must be held all the way
- Roof stops partway when closing and reverses as if something were trapped
- Roof left open in the rain because the close command is ignored
- Erratic operation that worsens in wet weather
Likely causes
- Close contact worn, dirty or stuck inside the sunroof switch
- Water from blocked sunroof drains reaching the switch and the console connector
- Open, high-resistance or shorted close signal wire in the headliner
- Console connector terminal corroded or backed out
- Poor overhead console ground affecting the switch reference
- Module reading an unreasonably long close request from a stuck button
- Sunroof module input failure
How to fix it
- Watch the close switch status in live data with nothing pressed
- Unplug the switch and see whether the input returns to inactive
- Measure the close contact resistance at rest and pressed
- Remove the overhead console and check for water, corrosion and green terminals
- Clean the sunroof drain tubes and dry the console area
- Continuity test the close signal wire and verify the console ground
- Replace the switch or repair the wiring, then reinitialise the sunroof and confirm full travel