Nissan: ECU codes from '96 Cefiro - how????

The engine decided not to start, from cold, on Christmas
morning in my '96 V6 Cefiro and the orange "Engine" warning
light is on.
It has the VQ30de 3 litre engine and it cranks over just
fine but will not fire.
How do I get the self diagnostic codes out of it to find out
what is causing the problem.
I found this site for the Maxima at
http://vbxmaxima.8m.com/ecu.html and my 'puter is identical
but the side where the Self Diagnostic Selector screw should
be is blank so I assume there is some other method whereby
the codes are extracted.
Any help would be much appreciated.