Last week I replaced the heatercore on my 04 one hell of a job done it in 12 hours tho but anyways I got everything put back together started the car up ran fine for about 15 min drove up the driveway no problems went inside got something to drink cane back out put it in reverse and it died started it back up went backwards about 10 feet and the vsa light and abs light came on and went into limp
mood shut it off then re started it went about a mile and went into limp mood again shit it off this time and restarted it went a lil way and the engine light started flashing and it was missing like crazy made it home it was late so didn’t mess with it came out next day and the car just cranks and won’t start I’m gonna check and see what codes it threw today but and advice or pointers where to start

 

Maybe something didn't get plugged in.

Maybe a ground is missing.

Maybe the heater core is leaking onto the PCM.

 

it's like you did all that work, but dont want to troubleshoot your own mistakes!

Get back IN THERE and find what's not connected.
Go back over EVERY inch of your work.
that's what I would do, anyway.