Can anyone tell me, because I'm new to mach3, these commands don't work for me.
I have output 2 enabled.

I type into the run box on the diagnostics screen M10P2 and M11P2 nothing happens. I expect 1 of the output leds to illuminate.

Is there some other setting I need to alter?

Those commands only take effect at the instant of axis (any axis) movement.

For example, the Gcode;

G0 X0

M11P2
G0 X1

Would turn ON Output #2 at the instant axis X starts to move to position X1 and;

M10P2
G0 X0

Would turn OFF Output #2 again at the instant axis X starts to move to position X0.

There are more details here;  http://www.cooperman.talktalk.net/files/27_files/Page652.htm
http://www.tweakie.byethost10.com/27_files/Page652.htm
 
Hope this helps,

Tweakie.

EDIT;  Link updated.

Thank you that helps a great deal.
I didn't understand the full context.

Tweakie thanks
I have just tried those codes this evening but without success.

I even cut and pasted your code in the post to a file and ran it.
The line after M11P2 didn't appear in the Mach3 code window and output 2 remained dormant.

On the plus side I read though your website and was very impressed with all you have done, both construction of your machine and products made on it.

A couple of points that may help...

All Mach3 Gcode must finish with a CR so it is usual to insert a null character such as % at the end of every file. If you do not do this then the last line of code will be ignored.
The Diagnostic LED's do not always work as expected so a Meter (or similar) connected to the mapped Output Pin may provide a better indication.
You need to be using Mach3 version .056 or later.

Tweakie.