What does it mean?
B2404 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Steerin Unit Communication. (function code) .
Symptoms
- Steering wheel volume, track and telephone buttons do not respond
- The audio changes volume or skips tracks on its own
- One group of buttons works while another group is completely dead
- Function returns momentarily when the steering wheel is turned
- Horn or cruise control faults appear at the same time when the clockspring is damaged
Likely causes
- Cracked or worn clockspring ribbon breaking the steering wheel control circuit
- Failed resistor network inside the steering wheel switch pad
- A sticking button holding a fixed resistance on the signal line
- Corroded or loose connector behind the steering wheel or at the audio unit
- Wiring damage following airbag, clockspring or steering wheel replacement
- Short between the switch signal and ground or another circuit in the column loom
- Faulty input inside the audio unit or the module that measures the switch resistance
How to fix it
- Watch the steering wheel switch value in live data while pressing each button in turn and record which ones fail
- A value stuck at one step with no button pressed indicates a shorted switch or a sticking button
- Disconnect the battery and wait the specified time before working near the airbag, then remove and unplug the switch pad
- Measure the resistance of each button at the switch connector and compare it with the manufacturer table
- Check continuity through the clockspring while turning the wheel lock to lock and watch for dropouts
- Inspect the column connectors for corrosion and pushed back pins
- Replace the switch pad or the clockspring according to which side fails the resistance test, then verify horn, airbag and cruise functions