Have installed new sony cd player into 1997 EL, there is power to the unit but no sound, do I need to put the security code in

TBH, I don't think so. My Kenwood KDC-MP433 head unit has a security code option and it doesn't need to be inputted for the HU to work. Did you connect the wires correctly? Positive to positive, negative to negative from the speaker to the speaker wire? Thats a common mistake people make when wiring everything up properly. Just double-check.

Some wires will have a stripe down both wires which confuses a lot of amateurs which is positive and which is negative. The darkest stripe tends to be the negative wire and the one with no stripe or a yellow/white stripe tends to be positive.

Wiring the speaker up in reverse will still give you sound though.. It just reverses the polarity.

your speaker wires may not be connected right...like rear negative connected to front negative with positive from another end. If all wires are in their rightful place, the speakers may be stuffed (probably not) or there are some loose connections behind the HU.

hope you get it up and running.

phong =P~