2004 Renault Trafic 1.9dci

Problem with Stop and Battery light staying on. Alternator output excellent lent . Checked output which is 15.5+ and stays when loaded. Checked output current to battery and is fine at 8 amps+ when loaded. Also put scope on out to check for DC and see if any a/c component. None. So I am struggling to get a confident check on beige w ire on alternator plug. Where does it go and where does it join the violet wire before the instrument panel. Any smart checks I can do. Help
Chris