I have a 2003 chevy silverado V8 4.8L 4x4
90K miles on it.
No leaks. Very good shape.

2 week ago, the engine light came on driving on the freeway.
Next day i drove to an autoparts store to have the engine code error checked.
Before I got to the store, the light was not on anymore.

Last week, the light came on again. It stays for 2 days.
Same thing, I was gone go and have the the engine codes checked.... light came off.

Thats sucks.

What could it be? that is really strange.

I was thinking on replacing the O2 sensors. I was told to do it when you get close to 100K miles.

Cheers,

 

Should still be stored in the computer. Have them check it anyway to see. Could be a number of things from O2 sensor to gas cap to spark plugs etc...

 

It could be an emissions related code, make sure to check your gas cap for a good clean snug fit...
and as 6LCHEVYZ71 said the code is still there even if the light is out, the light out means the fault condition is not present...
and you could be on the right track with the O2 also but I'd check the codes before shotgunning parts just yet....
If you have more then one code, write them down, have them cleared and see which ones come back and go from there...