What does it mean?
B1403 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Front Left Audio Speaker Output Circuit Open .
Symptoms
- Complete silence from the front left speaker while the other speakers work
- Fader and balance test shows the front left corner is dead
- No crackle or distortion, just no output at all, which distinguishes an open from a shorted speaker
- Sound may return briefly when the door is moved, if the break is in the hinge boot
- The rest of the audio system operates normally
Likely causes
- Front left speaker voice coil burnt open after long term overdriving
- Speaker connector unplugged or half-fitted after door trim, window regulator or speaker work
- Broken conductor in the driver door harness inside the rubber hinge boot
- Corroded speaker terminals after water got into the door, eating through the connection
- Terminal pushed back in the amplifier or head unit plug
- Aftermarket speaker adapter or wiring harness that was never properly connected
- Amplifier output stage failed open
How to fix it
- Fade fully to the front left and confirm the channel is completely silent
- Remove the door trim and check that the speaker connector is fully fitted and its terminals are clean
- Measure the speaker voice coil resistance across its terminals; an infinite reading means the coil is open and the speaker needs replacing
- If the speaker is good, check continuity of both speaker wires from the amplifier plug to the speaker connector
- Flex the harness inside the door hinge boot during the continuity test to find a break that only opens when the door moves
- Repair the broken conductor with a crimped and sealed joint that will tolerate the door movement
- Replace the amplifier only if the speaker and the wiring both test good and the output is still dead