2003 Chevy Suburban diaignostic connectos dead

This problem comes with cold weather, it starts fine then after apx. 30 to 45 seconds, starts chuging like its loading up, if you go into drive, its very bad, I took to 2 different places and they hooked scan tool up, and both said the tool would not read connector, I replaced the m.A.P. And mas air flow with no change, can tyou advise, I have checked all fuses, Thanks