Automatic Headlight Sensor Circuit
2000-2006 Lincoln LS 3.9L V8
Description
Malfunction in the automatic headlight ambient light sensor circuit.
Symptoms
- Auto headlights not turning on in tunnels/darkness
- Headlights on in bright daylight
- Auto headlight feature disabled
- Dash light sensor not adjusting brightness
Common Causes
- Faulty ambient light sensor
- Sensor covered by dashboard object
- Wiring damage
- BCM auto-light module fault
- Sensor window dirty
Diagnostic Steps
- Check light sensor reading with scan tool
- Clean sensor lens on dashboard
- Inspect sensor wiring
- Test BCM auto headlight output
- Verify feature is enabled in settings
Repair Notes
Replace ambient light sensor or clean sensor window. Check that nothing is covering the sensor on the dash top.
Related Codes
Other Body Codes
- B0001Driver Frontal Stage 1 Deployment Control
- B0002Driver Frontal Stage 2 Deployment Control
- B0003Passenger Frontal Stage 1 Deployment Control
- B0004Passenger Frontal Stage 2 Deployment Control
- B0005Driver Knee Airbag Deployment Circuit
- B0006Passenger Knee Airbag Deployment Circuit
- B0007Rear Left Side Airbag Deployment Circuit
- B0008Rear Right Side Airbag Deployment Circuit
- B0010Driver Side Airbag Deployment
- B0011Driver Side Airbag Deployment Circuit Open
B2100 on Other Vehicles
Lincoln Aviator
2003-2005 4.6L V8
Lincoln Aviator
2003-2005 4.6L V8 DOHC
Lincoln Aviator
2020-2024 3.0L Twin-Turbo V6
Lincoln Aviator
2020-2024 3.0L V6 Twin Turbo
Lincoln Aviator Grand Touring
2020-2024 3.0L Twin Turbo V6 PHEV
Lincoln Aviator Grand Touring
2020-2024 3.0L Twin-Turbo V6 Hybrid
Lincoln Aviator Grand Touring
2020-2024 3.0L V6 Twin Turbo Hybrid
Lincoln Continental
2017-2020 2.7L EcoBoost V6
Common Questions
What does code B2100 mean on a 2000-2006 Lincoln LS?
B2100 stands for "Automatic Headlight Sensor Circuit". Malfunction in the automatic headlight ambient light sensor circuit.
What are the symptoms of B2100 on a Lincoln LS?
Common symptoms of B2100 include: Auto headlights not turning on in tunnels/darkness, Headlights on in bright daylight, Auto headlight feature disabled, Dash light sensor not adjusting brightness.
What causes B2100 on a 2000-2006 Lincoln LS?
Common causes of B2100 include: Faulty ambient light sensor, Sensor covered by dashboard object, Wiring damage, BCM auto-light module fault, Sensor window dirty.