What does it mean?
B1683 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Rear Headlamp Leveling Sensor Circuit High .
Symptoms
- Headlamps remain in one position, often aimed high, and do not react to load
- Oncoming traffic is dazzled and other drivers flash their headlamps
- Headlamp system warning message in the instrument cluster
- No levelling sweep when the ignition is switched on
- The fault started after work at the rear of the vehicle or after a suspension repair
Likely causes
- Open circuit in the sensor signal wire or its ground return
- Sensor connector unplugged or a terminal pushed out, often after suspension or exhaust work
- Corroded terminals inside the connector that have lost contact completely
- Short to battery, or a short between the signal wire and the reference voltage supply
- Internal open circuit in the sensor after water has entered the housing
- Sensor link rod detached so the sensor sits at its mechanical end stop
- Failed input stage in the headlamp levelling module
How to fix it
- Read the sensor value on live data; a reading stuck at maximum suggests an open signal or ground
- Check that the sensor is still connected and that the link rod is attached, since a detached rod puts the sensor at its end stop
- Inspect the connector for pushed out terminals, corrosion and moisture
- With the ignition on, measure the reference voltage and the ground at the connector, then bridge the signal to ground briefly and watch whether the reading falls, which proves the wiring back to the module
- Test the signal wire for continuity to the module and for unwanted battery voltage
- Inspect the loom along the rear axle for breaks caused by stones, corrosion or previous repairs
- Repair the wiring or replace the sensor as the measurements dictate, then calibrate the levelling system and verify beam movement under load