I have a 1993 945T california car production date 1/93.

Check engine light started coming on when gas tank was approximately 2/3 empty. If I clear the fault and keep the tank above 1/2 it will go hundreds of miles without setting the code. Then when I let the tank get to 1/3 or less the code will set.

I had imagined that the problem was something in the in tank fuel delivery such as a leaking hose between the in tank pump and the fuel line causing air to get into the system drawn by the main pump and that the code would indicate a lean mixture rather than faulty O2 sensor. However the only code in the system is

2-1-2 "Signal missing/faulty from oxygen sensor Wiring fault to heated O2S sensor High fuel consumption, driving problems"

The sensor is at least 10 years 160K old so it certainly could have failed.

Questions
How accurate are the codes for something like this? The fact that the appearance of the code is linked to a fuel tank < 1/3 just a random event not linked to the in tank delivery system.

I really don't want to go through the effort of removing the in tank pump assembly if I can avoid it.

Thanks
Howard