2003 Pathfinder no power in D but revs in N and P ?

[Xabax]

Hello, I am having some real trouble with my 2003 Pathfinder Chilkoot. Recently the power has been cutting out on the engine in drive (D). It starts fine in the morning, I drive it for several minutes and then no acceleration in D when I press the accelerator pedal. This happened the other day as I was merging onto the highway and it freaked me out. The odd thing is that the engine is still idling and when I change gear (automatic) into P and N the engine revs like a champ. When I switch back to D pressing the pedal does nothing but will cause a momentary surge. My local mechanic said the battery was old and needed replacement so he installed an Interstate Mega-Tron II however the problem persists.I also have intermittent belt squeal due to cold weather (-20C) even though I changed the belts last summer, could this be related? Sometimes after the power cuts out it has trouble starting. It sound likes it doesn't want to turn over and the dashboard lights blink and click rapidly. I checked the battery's voltage right away and it reads 12.1 V so I don't think it's the cause. A towing guy told me it could be the distributor or the transmission. If this is the case why would it shift fine for 45 minutes and still rev great in N and P? Could the transmission computer be killing the spark to the engine in D? Any help is greatly appreciated as I have not come accross this problem before. Thanks.

[Buzzman]

Ok, first of all, your engine doesn't have a distributor, so don't listen to your tow truck driver.Secondly, with the engine running, the battery should be reading around 14-14.5 volts, not 12.You may want to start with having your alternator circuit checked, and go from there.My son's Maxima had similar problems, and after a so-called tech said he needed a new battery, the problem returned. It was actually the alternator. He wasted his money on a new battery.Good luck and keep us informed.