l hit the OD button on my shifter knob and when l do that, nothing happens.Should a light come on or something.How will l know when it is working.Thank You

Sometimes there are no indicator lights. l dont know if the extera has one or not. but generally you can tell if its on if you got past 45mph, the cars is going rev really high. generally its a matter of the button pushed in or not. see if that works

Well in my maxima the only light that ever came on was one to indicate that the overdrive was off. There was never a light to tell me it was on. But according to the owner is manual, when l would turn the engine off and then back on, the overdrive would automatically be re-engaged. But i'm not sure if its the same for your Xterra.