Here is what I got 92 civic VX. I was driving it the other day and the check engine light came on, Little green shift light stopped working, Idles faster, seems to have more power, and mileage has dropped from 47 to about 35. The code I am getting is 41. This points to the O2 sensor if I am not mistaken. The problem is that things costs like $350. 1) Is there a way to test this sensor before spending the money? 2) I have read about using other sensors and wiring them in. What will this cost me in Millage. I really like the 47 MPG I was getting. My sensor has 5 wires coming from it. Any help would be great.