03 Altima, all the sudden it won't start. Checked fuel pump and it's fine.

Hello, There are a couple of issues that seem to recur with Nissan which cause this symptom. The crankshaft position sensor and camshaft position sensor on these vehicles fail all the time, in several different engines. I recommend having the vehicle professionally diagnosed with a diagnostic scan tool and hands-on testing before making any parts purchases. This could be several other issues. Also, check your fuses and relays before shipping it off to the shop. You may find a bad one.