2000 grand Cherokee 4.0 o/d will not disengage is there a fuse or a relay I can disco
 

I have a 2000 Jeep grand Cherokee with a 4.0 the engine light stays on and the overdrive never disengages the button does not work anymore is there a fuse or a relay I can disconnect to just fix the problem because I will never use the overdrive

Never use over drive? over drive is 4th gear, even without realizing it you use over drive on a daily basis jeep or not, in basic terms over drive is any gear where the mechanical advantage of the transmission is optimized, making the engine do less work to achieve the same result, think when your driving on the freeway and your engine speed drops because you're at a sustained speed and not in need of power or torque. If you're driving around with over drive off your robbing yourself in gas. This also isn't a pull the fuse and be done with it fix, if over drive isn't disengaging you may have a trans issue

Actually overdrive is any gear that has a ratio of less than 1:1 where the trans output shaft is spinning faster than the input from the engine. 4th gear in your 42re is .69:1 qualifying it as an overdrive. If engaged with a 3.55 axle ratio, you should be running 1500 rpm at 55 mph with the torque converter lock-up also engaged. I think 3rd gear would be 2100 rpm.

You should check for trouble codes to find out why the light is on. It's possible it's a P0740, torque converter clutch not engaged. There is a solenoid pack inside the transmission pan that controls both the O/D and torque converter clutch. It could be a faulty solenoid or simply a broken wire or bad plug connection, IF that's the problem.