Background:
2004 Chevrolet Silverado RCSB. The truck was originally had a 4.8 that has since been swapped to an LQ4 6.0. I did not do the swap, bought the truck with the swap. The PCM and harness appear to be OEM.

Issue:
The truck is having an issue of the O2 sensors not switching at idle, but above idle and going down the road they do begin to switch. Upon looking further I discovered the O2 sensor heating element is not working.

Troubleshooting/Results Performed to Date:
I have confirmed all the wires and made sure they were run to the correct pin on the PCM. Also confirmed the heater circuit wiring from the PCM to the O2 sensor is good based on the following tests performed. I have continuity on the ground wire: Bank 1 Sensor 1 – blk/wht wire; Bank 2 sensor 1 = lt. Grn. I have continuity and voltage on the power wire: Bank 1 Sensor 1 – Pink 12.5 v; Bank 2 sensor 1 = Pink 12.5 v.
I created a test light that plugs in the O2 harness for the 12v and ground signal. The test light is made of an O2 pigtail, 7440 socket and 7440 bulb. This made it easier for me to see when the circuit would be active or not. With the test light connected, turn the key to the on position, engine not running, test light does not come on. I pulled the connector from the PCM and back fed ground from the battery terminal and the light will come on.
Tested PCM grounds with multimeter and confirming continuity from pin out to the battery ground cable as follows:
PCM Connector 1 (Blue)
Pin 1 – Ground circuit is good
Pin 24 – No wire in this pin out position
Pin 27 – I have a red wire in this position vs. blk/wht wire as expected per schematic. Checked for continuity and it did not check out.
Pin 40 – Ground circuit is good
Pin 64 – I have a green wire in this position vs. blk/wht wire as expected per schematic. Checked for continuity and it did not check out.
Pin 67 - I have a red wire in the position vs. blk/wht wire as expected per schematic. Checked for continuity and it did not check out.
Connector 2 (Green)
Pin 1 – Ground circuit is good
Pin 40 – Ground circuit is good
Tested the heater circuit of the O2 sensor with a result of 13 ohms

Next Steps:
I feel like I am honing in on my root cause but, just not quite there yet. I believe the issue is either the PCM or a ground circuit to the PCM that is causing my issue.

I have confirmed with two schematic diagrams from different websites to ensure accuracy of what I am referencing and that seems to check out. So, I am puzzled by Pin out 27, 64 and 67 on the blue connector having a wire that is not the expected ground wire coloring. Any guidance here would be greatly appreciated.

For pin out 27 on the blue connector I am tempted to run a ground wire to the pin out. I find it odd there isn’t a wire here. It does not appear a wire has ever been in this pin out location.

Before I go running wires or moving wires around, I am looking for direction or confirmation of my thoughts for next steps from you talented and experienced folks.

Thanks for taking the time to review my lengthy write up and for providing any insight.