2015 Jetta , starts up and runs fine and then every so often it does not want to start , I had mechanic check all the basics fuel pump , battery, alternator, starter and he could not find anything wrong even ran the diagnostic and no codes pop up . Car wouldn’t start for 2 days , I had it towed to the mechanic and I started rite up , he kept for 2 days and just started rite now problems . This is the 3rd time within 2 months that this pattern of problems happened. Any thoughts or ideas ?

SOURCE: 1995 toyota camry-stalling out when driving

You do not have to replace the fuel pump at a specific mileage.
I hate to speculate without physically inspecting the vehicle, but, my best solution here & now may be the fuel pump. Now, I would not go out & buy one before you had proper diagnosis. Here is one test, but you will need to have to experience the stall again, and then test to see if you have fuel pressure at the injectors. If you have no fuel pressure, replace the pump. Fuel filter issues do not "come & go", they stay, and your car would not run properly. Also, a fuel pump failure will not set a computer code on this particular model vehicle. Hope this helps..

SOURCE: 1998 Plymouth Breeze

change your sparkplug wires that will salve yor problem

SOURCE: My battery keeps dying but my alternator is fine

First, DON"T check your alternator that way anymore. It's not good to do on newer systems! The best, quickest check I can tell you is to put a volt meter across the battery. Running with accessories off you should see voltage of about 13.5 to 14.5.
With all accessories and headlamps on high turned on, it should not drop below 12.5. (and that is the absolute low end!).
It sounds like something in the car is staying on. check the glovebox light and interior light delay and make sure they are OK. Otherwise, you will have to start checking entire system for a draw that's taking out the battery overnight. To check, you can pull one fuse at a time and see if draw goes away, then check system that fuse serves.

SOURCE: i have a ford explorer 1996 it turns over but wont

I HAD THE SAME PROBLEM IT SPENT A WEEK IN THE SHOP AND THE CAR WOULD START EVERYTIME. I BROUGHT THE CAR HOME AND READ ALL I COULD ON THIS PROBLEM.
IT WAS THE IGNITION RELAY $7 TO $15 AT ANY PART STORE. IN THE MAIN POWER BOX ON THE DRIVER SIDE NEAR THE FIRE WALL (BACK WALL). GO AND BUY THE RELAY FIRST IT'S A LITTLE BLACK CUBE ABOUT 1" X 1" THE IGNITION AND THE FUEL PUMP RELAY ARE THE SAME PART. NOW REMOVE THE RELAY CLOSEST TO THE FIRE WALL THAT IS FOR THE FUEL PUMP. TRY TO START YOUR CAR. IT SHOUD TRY TO FIRE UP WITH THE FUEL THAT IS LEFT IN THE INGINE BUT WONT START. NOW PUT THE RELAY BACK IN AND START IT.
NOW PULL OUT THE SECOND RELAY FROM THE BACK. THAT IS THE IGNITION RELAY.
TRY TO START THE CAR, IT WILL TURN OVER BUT NOT FIRE AT ALL JUST LIKE IT WHEN WE HAVE THE PROBLEM ON THE ROAD. SO IF IT'S THE FUEL RELAY IT WILL TRY TO FIRE A LITTLE IF IT'S THE IGNITION IT JUST TURNS OVER. MY RELAY WAS A ORIGANL FORD SO THE UNDER SIDE OF IT WAS WHITE. PART OF IT WAS BROWN LIKE IT OVER HEATED. I TOOK IT APART TO CHECK TO CONTACT PIONTS INSIDE TO SEE IF THEY WERE BURT AND THEY WERE. CAUSING IT TO NOT MAKE CONTACT EVERYTIME AN NOT LETTING THE CAR START.
EMAIL ME IF YOU NEED HELP. [email protected]

SOURCE: 2005 FORD EXPLORER DIAGNOSTIC TROUBLE CODES 9318,

This really sounds like a problem with your battery. I know you said you checked it, but is it really putting out the appropriate voltage (12.66 volts) and CCAs? Even draining the battery once can damage it (especially in cold weather), and cold weather reduces the CCAs a battery can put out. A weak battery can cause those codes. When the vehicle hesitates to start, does that typically happen on colder mornings or after the car sat for longer periods of time? I would double-check your battery. If it's the original, it's near its end of life anyway.