Well…after more research & talking with my friend with the hp tuner software, not to mention nudging from a few board members… I FINALLY figured out the correct pin assignments to read the ECM!...
below is the obdii port pin out. This is for a E38 ECM from a 2013 chevrolet Silverado.
Pin 1 thru pin 3= empty
Pin4= signal ground
Pin5= chassis ground
Pin6= ECM pin28 (2500) tan/blk canbus(+)
Pin7 thru pin13= empty
Pin14= ECM pin27 (2501) tan canbus(-)
Pin15= empty
Pin16= batt. (+) const. power
For me I used pin J5 from the “X4” connector (640) red/wht wire for pin 16.
Thanks to
87chevy.com for the nudge to recheck everything again. I hope this will be a help to others and thank you all for the replies.