Try clearing the code by momentarily removing fuse 6, instead of using the button pressing procedure. Then double check to see that fuse 4 is passing power (only when running now) and your tank pump is working. If you are still setting the code for O2 sensor, measure the voltage at the junction between the sensor cable and the engine harness (the green wire connects to a black wire under a rubber boot). Make sure it is 0.5V when you first turn the key on, but varies from that after you have the car running a minute.