What does it mean?
B2504 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Warning indicator circuit open or short to GND .
Symptoms
- The right low beam remains lit when the lights are off or after the vehicle has been locked
- The lamp glows faintly all the time rather than lighting fully
- The module switches the right low beam off as protection and it stays dark
- A bulb failure or lighting fault message appears on the display
- Unexplained battery discharge when the vehicle stands overnight
Likely causes
- Right low beam control wire touching a permanently live circuit in the front harness
- Bridged terminals in the right headlamp connector caused by moisture and corrosion
- Ballast or driver from an aftermarket HID or LED kit back feeding the control wire
- Front loom pinched during bumper, grille or headlamp removal
- Insulation melted where the loom rests against the headlamp body or a hot component
- Trailer wiring or auxiliary lighting installation tapped into the right headlamp circuit
- Module output driver welded on internally
How to fix it
- Confirm the unwanted voltage by measuring the right low beam output at the module with the lights switched off
- Disconnect the headlamp and check again; voltage still present means the short is in the harness
- Examine the headlamp connector closely for corrosion between the low beam pin and its neighbouring supply pins
- Disconnect any aftermarket lighting, trailer module or conversion kit and retest with a standard bulb
- Follow the loom from the module to the headlamp looking for chafe and pinch damage, particularly around the front panel
- Repair the wiring with a sealed joint and secure the loom away from heat and moving parts
- Replace the module if the output stays live with everything downstream disconnected