I'm having another crack at this as my last posting fell stillborn from the press!
Has anyone tried to replace the radio on a C4 with an after market device? How were the ancilliary functions such as the trip computer and the rear wiper controls affected? Were you able to continue to use the central LCD display and how did you manage with the steering wheel controls?
I know there are devices to maintain the steering wheel controls but I wondered how well they work and whether they cope with all of the functions that the radio seems to cover.
It's not a simple job integrating the controls on the steering wheel into a different radio/CD head unit. The radio is connected to the vehicle's CAN bus (Controller Area Network
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and receives data from various parts of the car. The buttons on the steering wheel will be transmitted over the data bus and the radio picks these up and acts accordingly. The BSI will also transmit control packets over the data bus so the radio can adjust the volume as you drive the vehicle, or mute the radio/CD volume if the parking sensors are operating or Bluetooth handsfree kit is fitted and an incoming call is received. You have to remember that all the buttons on the steering wheel are all software programmable, I would be very easy for Citroen to recode the radio buttons to wind the windows up and down. If you have the non base model of the C4 you'll have the user programmable button on the steering wheel (hold it down for 2 seconds to program). You can use the button to switch the interior lights on/off, display the event log or dim the console lighting....
I don't know the exact details about the radio in the C4, but I would guess that the BSI interrogates and reads the current status of the radio so it can drive the centre console display allowing you to see details about the current radio station or the CD track been played.
I've just had a quick Google and I've found referenced to
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and this mentions VAN bus, I'm pretty sure that the C4 has only CAN networks (anyone confirm?) so I've not found any adapters that I think would work. So, yeah, all in all - not a simple job, but I'm sure someone will develop an appropriate interface eventually.
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