CAT C-12 Acceleration hesitation 3rd,4th,gears primarily

I have a 99KW Tri-dump heavy spec with a CAT C-12 , 10 speed, Truck starts every time and fast no cranking , runs out good , pulls good at first , with 15mins to 1/2 hr service engine light comes on in 3rd and 4th gear , truck hesitates , runs lousy until the light goes off and its fine until ya run through the gears again calling for power . Light comes and goes and does not stay on long just long enough to screw up the shift pattern when she needs the power . 3rd gear high range always the worst and has a total flat spot when the light comes on . I put a scanner on it and it does not store the codes that it may be throwing , any chance it could be a throttle control issue ? Fuel is clean and seems to be where its supposed to be , no starting or stalling issues and no problems ever not staying running or otherwise , no engine smoke other than severe cold but clears right up , no smoke pulling a load and she uses no oil , kinda dont know where to look next its frustrating when running heavy as the problem seems to magnify , thoughts are and would be welcome !