All-Wheel Drive Disabled

My 06 Uplander has the "AWD disabled" light on. From what I have read it is probably the differential check valve that is bad. I just changed the very expensive fluid and do not want to drain it to replace the valve unless it is necessary. So my question is can I just plug in a known good check valve to see if the fault clears, without actually installing it in the differential?
Thanks for any input.