Anyone know how to test a 7747 ECM? 5v or 12v for CES light?

[GOY]

Here's what I have:

No CES light when the ignition is on the on position.
Can't run codes. The light just plain never lights.

I've replaced the bulb with a working bulb. I've resodered the joints on the board for the light, and tested it on the board - it works when 12v is applied to it. (Didn't burn out bulb)

Here's the question - how should I go about testing the wiring/ecm for failure? My first thought was to pull the ECM, then apply the required voltage to the 5th pin (I think it's A5)... but I'm not sure if...

A) I should apply 5 or 12 volts
B) If I do that, will it work even then, or does that light share a common ground that requires the ECM to be plugged in too illuminate.

Any help on diagnosing a fried ECM or bad wiring?