I recently bought a 2004 Silverado with a 5.3 liter in it. I was hoping to get some suggestions on fixing a bad oxygen sensor circuit. I have a scanner tool and it detected a P054 fault. I also was able to display all 4 of the O2 sensor circuits on the tool and the voltage of 1 circuit stayed at about .450 volts. Let me tell you what I did so far. I did the usual easy fix and just replaced the per-converter sensor on the passenger side. I then checked the O2 sensors with the scanner tool and all 4 were working, meaning the voltages were all changing. About a week later the same circuit tripped another P0154 fault. So thinking I may have a bad circuit I took the O2 sensor I removed from blank 2 and put it in bank 1. It worked perfectly. I then took a multimeter and with the engine running and measured the voltages on the O2 connector coming from the truck. One side of the connector, the pink and green wires measured 13.7 volts. I think these wires are the power supply for the O2 heater. The other 2 wires, the tan and purple wires had no voltage in them. For a sanity check I measured the voltages on another O2 sensor circuit and the same 2 wires measured about .4 volts. I then disconnected the wiring harness from the PCM and connected 1 lead of my multmeter to the purple wire on the O2 connector and began to check the engine wiring harness. I had continuity in both the purple and tan wires. My thoughts are that the PCM itself may be bad. Is there anything I’m missing? I hate to have to take the truck to a dealer! Sorry for the long-winded post but I thought I should say everything I did so far.