Can you replace just one rotor when doing brakes, one is still like new the other is grooved from a bad pad?

 

If the other one is true and not scored, then yes, you can replace one rotor.

 

should have the other turned to insure that it is not warped in any way

 

Just replace them both. Rotors are relatively cheap. I have a 02' grand and it loves warping rotors. It 130k on it and needed turning like every other oil change. So I gave in and bought slotted/drilled ones, and these rotors have lasted 20k miles.

 

If you hand torque your wheels with a torque wrench you will not go through so many rotors. Turning them is only making the chances of them warping greater. Every time you remove metal from the rotors by turning them they will not be able to absorb heat and disapate it as effeciently. Hand torquing is the key to keeping the rotors from warping.

 

All 1999-2002 Grand Cherokee WJ models built through May 10, 2002 came equipped with brake calipers made by Teves. They are black in color with an open-sided bracket design. Due to poor caliper centering, the Teves calipers caused the rotors to warp, a problem that has plagued Grand Cherokees. At the very end of the 2002 model year, Jeep changed to "fully-closed" style calipers designed by Akebono. All Grand Cherokee models produced on or after May 11th, 2002 feature the new calipers. International models built on or after August 16th, 2002 also feature the new calipers.