Recently i found that mine 93 civic Cel light on once RPM>3000.I tried to jump the ECU, i found that it is code 48-LAF sensor. Does this mean the o2 sensor is not working properly? But why the cel light only on once the RPM >3000?
Just because the light isn't on doesn't mean the ECU doesn't have stored codes. You retrieve them by jumpering the two pin diagnostic plug in the green cover near the front passenger's right kick panel.