I don't know the year of this 7.3 said it's throwing code 6303 (on a Diablo).
Describes the problem as not shifting from 2nd to 3rd unless the throttle is "blipped".
Truck belongs to someone with no internet access at this time.

 

Never seen a code that high in numbers. Is this a tuned truck? Could it have been P0603?

 

Could be, I related that to him after looking up the codes in the tech area.
He hasn't got back to me yet.
I didn't see 0603 in the list, what is it?
Are you looking at a list other than what is in the tech folder?

Thanks Joe!

 

It's just a code that comes up when a tuner is installed. P0603 Internal Control Module KAM Error. Found it here:
Ford OBDII Diagnostic Trouble Codes - Powerstroke Diesel Codes .: Articles

 

P0603 Internal Control Module KAM Error
Nearly all chipped trucks have this code.
Edit: Joe's faster.lol

 

trans codes are p19xx

highest code I can find are 34xx