What does it mean?
B1478 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Channel 5 Audio Speaker Output Circuit Shorted Together .
Symptoms
- The channel 5 speaker falls silent
- The amplifier shuts the channel down or puts the system into protection mode for a moment
- Audio cuts out at higher volume and comes back when the level is lowered
- Amplifier housing becomes warm after a period of use
- Code sets within seconds of the audio system being switched on
Likely causes
- Loom crushed by a trim clip, screw or seat rail, letting both conductors touch
- Insulation worn through where the pair passes a sharp edge or a body grommet
- Bent spade terminal or a stray strand bridging the two connections at the speaker
- Corrosion or water inside a connector joining the two pins
- Leads twisted together or joined at a poor splice during an aftermarket installation
- Internal short inside the speaker
- Damaged amplifier output stage producing the same reading
How to fix it
- Confirm the affected speaker with fader and balance
- Disconnect both ends of the circuit and measure between the two output wires with the speaker unplugged; a near-zero value proves a harness short
- If the harness is clean, measure across the speaker terminals and compare with the specified impedance
- Remove trim along the route and look for crush marks, screws through the loom and chafe at grommets
- Inspect both connectors for bent spades, loose strands and green corrosion
- Repair the damaged section, insulate it properly and secure the loom clear of the crush point
- Replace the speaker only if it measures shorted on its own
- Clear the code, play the system at normal and high volume and confirm the channel stays on