HAVE A 2007 NISSAN XTERRA CHANGED THE BATTERY BUT THERE IS JUST A CLICKING AND WONT START. USUALLY AFTER A DAY OR SO. IT'LL START AGAIN AND BE GOOD FOR A WEEK OR SO BEFORE ACTING UP AGAIN

You tube it you must did something wrong

Probably your charging system is not working. Auto parts store may help you determine problem.

It will be on the dashboard usually looks like a padlock. The ecm needs to be coded to the key and possibly to the car other ecus and dashboard as that is usually the canbus controller . If u have only changed the ecm the car will not start

battery is dead, check the battery and charging system.

It's your starter thats bad

When you try to start does the motor spin but wont start or is there no noise at all, if its no noise at all then i would start by checking the starter and if it spins but wont start then try holding gas pedal down and cranking the motor with a dead battery it may have lost memory and will need to run awhile to relearn idle at start up and other readings you may need to hold gas pedal to keep running for a few minutes,start with this first.

Clicking and not turning over is caused by weak battery, loose or dirty battery cable clamps or loose connections to starter.

SEE IF SOME ONE CAN GIVE YOU A HOT SHOT YOUR BATTERY MAY BE WEAK AND THAT CLICKING NOISE IS THE SIGN OF NOT ENOUGH JUICE GETTING TO THE STARTER

Check the battery cables at the termnials.

The fuel pump died out .
Replace the fuel pump , sometime they give no warning .

Good Luck