OBDii connector

[rodstored-72]

hi, I am trying to wire my OBDii connector and I am confused on what wires to connect. I have a 1986 C10 with a 2013 4.8LS stock engine. I have found the 2 data wires from the ECM (circuit 2500,2501 - tn and tn/blk)
1) tan/blk=2500 data 12v +
2) tan=2501 data 12v -

my OBDii GM connector:
1) pin 2 purple (data wire?)
2) pin 4 blk chassis ground
3) pin 5 blk SIGNAL ground
4) pin 16 org 12v constant on

this is my thought (understanding) of the connections:
A) conn pin 2 = circuit 2500 tn/blk wire (data 12v +)
B) conn pin 4 = ground to chassis
C) conn pin 5 = circuit 2501 tan wire (data 12v -)
D) conn pin 16 = connect to constant on power

I am just not sure on how & what to connect to install the OBDii connector?

any assistance would be greatly appreciated
thanks!