I have a 2003 f-150 4x4. First off my abs light came on and i started hearing a lound grinding noise only at 40mph, So i finally figured out it was my hub assembly. (getting it fixed in 2 day) any how but shortly after my abs light came on i tried using my 4x4 and and nothing happened. It is in the fly, when i turn the **** nothing happens no lights on the dash come on no nothing. I heard of someone having a bad hub and there 4x4 stopped, reason being i guess it lost vacume, but dosnt really make sense b/c i would think that the lights in the dash and would still come on but maybe hteres a sensor that shuts the system down. Does anyone have any thoughts or know what what it might be. I just cnat see the switch or 4x4 motor going out at the same time the abs light came on but idk. Any info would eb highly appriciated.

 

You do not have hubs other than regular bearings. It engages the front at the diff. If you are not getting a light when you turn the dial, the first place to look is the GEM module or the switch itself.

 

If no light is coming on, then it's definately electronic. I would do as kingfish51 says.

 

Thank you for your help! Where is the GEM modual located?

 

Believe it is on the back of the fuse box. Check for corrosion.