G35 not starting up?
 

Today I was doing a idle relearn on my 03 g but the next time I go to turn it on everything turns off. I’m pretty sure it has to do with the alternator. I already changed the starter and battery on the car. Hopefully you can help me out. Thank you.

Alternator does not aid in the starting of the car. Only after the car starts does your alternator become of use. Are your battery cables tightened correctly?

Did it even try to crank? If not then test the battery, verify the cables are good and clean.

Ok I did move around the positive cable of the battery and it worked!

Ok, take the connection apart (negative side is the first to take off and the last to reinstall) then take a wire brush and clean the metal contact areas very well. Those purpose-mafe spark plug cleaners work excellent. Once it's all down to SHINY METAL apply a small amount of anti-oxidation grease and put everything back together.