Testing 02 Explorer 4x4 module

[fox4ford]

Does anyone know how to test the 4x4 module? My X is an 02 and the 4x4 light on the dash comes on when I start the engine, but when I try to engage the 4 wheel drive nothing happens, no light in the instrument cluster and no light on the switch for low range. I tried the module out of my brothers 02 X which worked perfectly in his X, and no difference. Then I put my module in his X and nothing worked. So I put his module back in his X and nothing worked!!!!!!!
I'm not going to throw modules at these things without finding a way test them to find the problem. Any ideas?

 

[fox4ford]

So nobody test these things? They just replace the modules and hope that cures it?

 

[fox4ford]

Surely somebody knows how to test the sensor inputs and the module outputs. I burned up one good module and don't really want to burn up another. Thanks

 

[fox4ford]

Anybody?????????????