Nissan Maxima 2003 - Engine stops immediatley after start

Could be the ignition switch, the ignition circuit that goes to the positive terminal of the coil.

Try this turn key to On and check for power at the coil-do you have it.

Or you can do this take a wire hook it up on the positive terminal of the coil and the other wire end to the battery positive terminal-this will bypass the ignition circuit-also you will see all the lights that normally comes On. Now try to start it.