I asked if someone could help me to identify the correct pin ...
There is a difference between identifying the correct pin on a diagram and then finding it on the corresponding PC board. I have a feeling that you have not found it and this sad excuse for a schematic/wiring diagram is no help.
I figured pin 5 (on J5) on the shield was the correct pin.
I agree. What makes you think that you have your yellow wire in the correct place.
Don