Hello again Scotty,
About 7 months ago I asked for your thoughts regarding OBDII O2 codes for my sons Toyota Avalon. After hearing your thoughts and checking everything I could think of, I never was able to resolve the issue. The only thing I hadn't tried to date was to replace the PCM.
However, my son's Avalon has now developed a new problem. It turns over but doesn't start. Energy is reaching the spark plugs and I can hear compression. What I don't see/hear, is the fuel pump when I turn the ignition switch. I've just started investigating, so there are some basic things I have to inspect, such as the fuses and relays. Additionally, the fuel filter appears to be the original, so that's definitely the first item I'll be replacing after 190k miles, lol. However, thinking back to issue with the O2 sensor codes in combination to this new problem, I notice the OBDII codes for the O2 sensors are no longer present, and there are now multiple misfire codes in their place.
Could the previous O2 sensor codes be a symptom of a failing fuel pump or clogged fuel filter due to the restricted fuel supply?