How do you fix a Citreon c2 car stereo problems?
Answers:
In short no!
Do you still have your Citroen radio because you really need it? Unfortunately the car you have has what we call "multiplex wiring", which in short means that the stereo is interlinked with your car electrics. As you mentioned your central locking, speedometer and diagnostics are linked in with your stereo. This is because if Citroen wanted to diagnose a fault it can be shown through your stereo display!
This means that you can't fit another stereo even though the connections at the back may seem ok.
If I had to make a suggestion for you, Get yourself an FM modulator or in Halfords they call them the "denison" or "Harman Kardon" kits for ipods and auxiliary adaptor. Even though you can't play Cd's you can plug an mp3 or ipod to your existing stereo and allow you to have increased connectivity.
If your after a system build you have to do some major rewiring to connect amps etc to this unit but it can be done ! (I've done it before). The down side is if the car is brand new and you mess around with the stereo they can void the warranty for the ENTIRE car!! (Be warned!!)
But you have got some options so speak to your local specialist and give it a go! Good Luck