testing with multi-meter

Hi,

When an axis (x-axis) suddenly fall silent, how does one goes about
trying to locate the fault?

This is what I have done:
1. interchange motors (x-axis driver side still silent)
2. change another driver (all axes OK)
3. Peep at Gecko's power LED (all LED on)

This seem to show that the problem is either within the x-axis Gecko
(unlikely) or in the connection from the Gecko to the connector on
the panel. Physically everything seem OK. Electrically/electronically
how does one test without a scope, with just a digital meter?

Thanks

Andrew