The overdrive light blinks/flashes constantly.

Check the transmission mounts perhaps the assembly has been put askew by a few degrees...butyl rubber degrades inside of five years...hopefully they used a urethane black...but if they did not you're going to have to change the transmission/engine mount~

The blinking means your transmission is in safe mode. I found this which might help.....http://www.nissanclub.com/forums/general-nissan-altima-discussion-1993-2001/169955-o-d-off-light-flashes-why.html

I own 2007 Nissan Sentra with 70k miles on it. The overdrive light blinks/flashes constantly as I drive. The faster I accelerate the faster the O/D light blinks/flashes and the car jerks as well but when I hold the overdrive button constant, the light goes off and the jerking stops. I have recently changed the transmission fluid with CVTNS-2 but I have still not found any solution. One other bad effect I have experienced is that the car has started consuming fuel but I do not know whether is as a result of the O/D light blinking. I need help!!!!!!!!!!

@Dwomoh would chase the end of the black 1/0 cable as it attaches to ground and clean it with a wirebrush and the spot where it bolts to...get good solid ground your problems should go away.~

thanks a lot roy but I still do not understand your answer

My answer is that ECU's need to have solid ground to behave correctly...not intermittent...flashing..."brown power" makes illegitimate things appear....the OD control is affected by BAD ground...you have nothing to lose by unbolting the main lug and cleanin' it down to shiny...establishing a solid ground connection...still don't understand your question...

the o/d light flashing means there is a problem with the cvt. cleaning the ground may help (black wire that goes from the body to drivers side of transmission). but most likely will have to get diagnosed at dealer. may be warranty if you got the extended asp or if there's a recall on it but I don't think there's a recall on those. may even be able to reprogram tcm at the dealer the cvt's rarely fail mechanically.