to all who might have an answer, the other night i was changing the O2 sensor on the wifes altima and i saw that the negative battery cable had corroded off of the terminal to attach it to the motor. car still runs fine, but the ses light had been on (reason for O2 sensor ) i re-attached it best i could and waiting to get new cable, but wondering if that did any damage to the alt./charging system ?

Mike

I am not a big Nissan guy, but I do work on Japense cars for a living even though I don't own one.
It is possible that a weak connection could cause your alternator to overwork itself. However, if the batt/charge dash light is not on, you are probablly ok. The only way to tell for sure is to have it checked by someone who has a machine that can check the alternators output on the car while it is running. This will tell the alternator's amperage and voltage output as well as check for bad diodes.
Replace that bad ground and see what happens.
I once say a car with a bad main ground cable melt some smaller wires as the current looked for a path to ground. This probably occured while the starter was engaged-big current draw!
When ever you disconnect the battery the stored codes in the computer will be cleared.
What is the "ses" light you are referring to? What year Altima? A little more info. would help.

I
When ever you disconnect the battery the stored codes in the computer will be cleared.
What is the "ses" light you are referring to? What year Altima? A little more info. would help.

thanks for posting, 02 altima and the service engine soon light soon says code 420 or "P0420 according to dealers"
light has not been on in 2 days, maybe that was it?

Code P0420 can be caused by bad catalytic converters, O2 sensors, and a bunch of stuff. Often replacing an O2 sensor does the trick. It is way cheaper than a cat. It takes 3 warm-up/cool-down cycles to make the computer happy. If you've done that and the light stays off you've fixed it.
Sometimes that stuff is hard to diagnose. I'm glad my personal cars are not computer controlled.

thanks for the help, going to do the sensor this w/end. it is certainly alot cheaper than a new converter.
Mike

How many wire are coming out of the O2 sensor? If it's a 1 or 3 wire sensor, then a bad engine ground will massively screw up the computer's readings of the O2 sensor. If it's a 2 or 4 wire, then one of the wires is signal ground and it shouldn't affect the O2 sensor reading, unless the engine and alternator are pulling ground back through the signal ground, in which case there is no telling what it would screw up and/or fry :).

__________________
Mike, supposedly 69 350 SS
BTW, why aren't you sure if your Camaro is a 69? :)

If an emissions problem happens before 100K miles, isn't it covered by Federal emissions? Free of charge to consumer?