I replaced ignition module on 2003 xterra, now it won't start. It ran before i changed it.

SOURCE: Starter fails to start.

I'm having the same problem. The dealership keeps telling me it's the starter. I've replaced starter and still have the same problem. I have had all the wiring and new key swith put in and still have the same problem. I guess were in the same boat!!!

SOURCE: removing a timing belt on a 2003 xterra

If you have a 3.3L engine, this is know as an interference engine. That means if the engine is running when the timing belt breaks or strips its teeth, the lower part of the engine brings the pistons up and they hit the top end of the engine bringing the valves down. The two sections then interfere with each other and your wallet at the same time. The valves bend when they smack the pistons and the engine will need a head job as a result. A mechanic can confirm the damage with a test called a cylinder leakdown test. It sounds like you will have more than a timining belt needed at this point.

SOURCE: I have 2000 xterra, bad fuel pump?

check manual for a fuel system reset switch .good luck

SOURCE: 2003 Cuts off when hot, will not start untill cool

My 2003 nissan sentra would get hot and stall out even in middle of highway doing 70 mph. The guages would go up and down. Would not start up all the time after stalling. had to cool down first. Nissan said it was head gasket, and wanted to charge 1000.00 for the job. I took to local dealer who charged me 550.00. Works fine ever since. Nissan dealer said they do like 3 head gaskets a week on the sentras. They have crappy ones in original parts. They have not recalled though.

SOURCE: the oil light came on today when i started my 2003 xterra

The oil light comes on when there is no pressure. There is no pressure when the pump either cannot get oil to pump or has oil and will not pump it.

Get it checked before you do anything else. A engine running with no pressure is a cooked engine.