No check engine light and truck won't start?

No check engine light.  Have all the issues you guys are having plus some.  
Changed the coil, spark plug wires, cleaned the grounds, new battery, new
computer and it was flashed.  Ran for a day really really well, now it won't
start and hasn't in a couple of weeks.  Fuel pump engages but now the
check engine light won't come on.  When the check engine light did come on
the fuel pump engaged and would start.  Couldn't keep it running for long but
it did start.   Has power and all that crap but what's the deal with the check
engine light now?  This is so damn frustrating as I've been dealing with this
for a year. It seems that everyone that owns this year of truck or around this
year is having same issues.  

This problem started last summer driving down the highway at 80 MPH
pulling my utility trailer the truck died.  It has continued to do this except
when it's cold outside and when I say cold I mean 60 degrees or colder.  Any
temperature higher it dies.  Used to be able to reset the computer by
unhooking battery cables and all that crap but not anymore.  Ordered a new
computer and yes it was flashed, installed it and it ran great for one full day.  
Now it hasn't started in 2 weeks.  Changed the coil, spark plugs and wires,
new battery, cleaned the grounds, check all the electric everything is in
check.  Even changed some fuses.  Now the truck would start the other night
when turned to on position check engine light came on and fuel pump
engaged and would start.  Wouldn't stay running \very long but it started.  
Now, NO CHECK ENGINE LIGHT and no enganging of the fuel pump.  
HELP PLEASE, or I'm driving it into the river.