What does it mean?
B2405 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Steerin Unit Communication. (rolling code) .
Symptoms
- Sound cuts out after a period of playing and returns once the unit cools
- The display shows a heat or protection message
- One or more speaker channels drop out before the unit shuts down completely
- The head unit is hot to the touch behind the dash
- The fault appears much sooner at high volume than at low volume
Likely causes
- Restricted airflow around the head unit from a blocked dash cavity or added insulation behind it
- Internal amplifier stage running hot because a speaker circuit is partially shorted
- Speaker wire shorted to ground or to another channel, loading the output stage
- Clogged heatsink or a failed internal cooling arrangement
- Supply voltage too high because of a charging system fault
- Faulty internal thermal sensor triggering a false shutdown
- Extended high volume playback in very hot ambient conditions
How to fix it
- Reproduce the fault and note how long it takes, since a load related shutdown appears far faster at high volume
- Measure each speaker circuit for a short to ground and for a short between channels at the head unit connector
- Check every speaker for a shorted voice coil by measuring impedance at the speaker terminals
- Verify charging system voltage is within specification with the engine running
- Check the head unit mounting for blocked ventilation and remove any padding added behind the dash
- Confirm the audio unit ground connection is clean and tight
- Replace the head unit only once the speakers, the wiring and the supply have all been proven good