So, I replace the O2 sensor on my '97 2.3 N/A because of a CEL light and code 133. Drove for 30 miles and the CEL comes back, but with no code. This code has come and been reset 5 times in the past year and always read no code. Autozone got a 133 with their scanner, so I just replaced it. I have the same situation as before the O2 sensor replacement. Bank 1 (upstream of the catalytic converter. Any suggestions or advice?