What does it mean?
B1575 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Automatic Lighting Sensor Circuit Malfunction .
Symptoms
- Parking and tail lamps do not switch on, stay on, or come on at the wrong time
- Automatic headlamps turn on in bright daylight or fail to turn on at dusk
- Dash illumination brightness behaves oddly and does not follow the switch
- Lights-on warning chime is missing or sounds constantly
- The code sets again every time the light switch is operated
Likely causes
- Worn contacts inside the headlamp and parking lamp switch, so the park request never reaches the module cleanly
- Corroded or loose connector at the light switch
- Park lamp input wire chafed or partly broken behind the dash
- Failed automatic lighting sensor on vehicles where the module takes its lamp request from that sensor
- Poor module ground giving a false or unstable input level
- Body module input stage failure
- Damage from a previous dash, radio or accessory installation in the light switch loom
How to fix it
- Watch the park lamp request in live data while moving the light switch through every position
- If the input never changes, test the switch for continuity at its own connector before replacing it
- Confirm module supply and ground with a voltage drop test, since a poor ground alone can create this code
- Inspect the loom behind the dash where it passes metal brackets and the column
- On the automatic lighting variant, cover and uncover the sensor on the dash top while watching its live value, and check its connector for a bent pin
- Replace the light switch or the lighting sensor only after it fails a direct measurement
- Leave the body module for last, and check for a software update before replacing it