OK so i have driven my car for a about 3 months with out either of my o2 sensors. I have not had my downflow sensor in since a pretty much got my car about a year. Now i have had a cel because of the o2 sensor the whole time. I still do not have my upflow o2 sensor in but yesterday i put my downstream one in and my cel turned off. Why is it not throwing a code for my uopstream????? BTW its a 94 obd1.5
