3 toy trucks I've kept for 2 years to give for this Christmas will not work.

ha thanks.ve you tried searching for GROUNDED wires ?

Take it an have vehicle scan done . Your vehicle has a vast amount of electronics , control modules , communication networks for the modules to share data on . All it takes is one of the wires touching ground to cause all kind of problems . There are modules inside the doors that control power windows , locks , mirrors etc. . Hooking up a scan tool that can check for communications from all modules . Not a code reader . A GM factory Tech 2 would be best . I work for Cadillac ,have for twenty years .

What year and which engine ?

You have worn front end parts or the tires have a separated cord in them.

is the check engine light on?

i believe there are 2 alternator's for that 5.3 i think you need the one with the higher amps. I had the same problem and went with the higher amp alternator and i have not had a problem that was 3 years ago.

I've had this issue myself on my own Pathfinder. Remove the negative terminal first. Look at the 2 connections that are on the positive post.There are 2 spade connectors.Remove and clean with a wire brush and then reinstall the 2 connectors and then the negative terminal. This should fix it. Radio making a buzzing noise that goes up and down with the engine RPMs? Let me know.

I'd run it by Autozone if this was the batter that was in it when the alatnator went out it may have cause the batter to get a bad cell, they will check it for free, Most batters have a 3 to 5 yr. warrenty. DONT tell thim your alatnitor went out if the battery showes bad this will void the warrenty just simpley say my batter has a bad cell....of corse the place you bought the batter will test it as well befor they give you or pro-rate your old battery good luck

po420 is catalylic converter system efficiency below threshold, which means converter is not burning or cleaning exhaust good, i ve found that 90% of the time its bad o2 sensors they give off a false reading to computer, replace the frt and rear o2 sensors and reset engine light that should take care of problem, if cat con verter happens to be no good its no loss because new o2s should be replaced with new converter, but i think o2s will solve youe problem. hope this helps.goodluck.

sounds like you are putting a bad battery into the car...try a fresh battery.  Batter is spelled...battery