O2 sensor - whats a normal reading

[Thassos]

Im trying to locate a fairly infrequent OBD code, on a petrol engine using a cheap OBD tool its giving me P0420 codes (inefficient cat?) i was able to have a look at the 02 sensor voltage and it seems to jump around a lot from 0.05v to 0.8v ish even when the engine is idling when driving if you take your foot off the accellerator it drops to 0v, but over a period of say a second when crusing it show big step jumps say 0.1v to 0.4 to 0.9v etc so im wondering if this is normal behaviour for an O2 sensor.

[nickar]

Originally Posted by Thassos

Im trying to locate a fairly infrequent OBD code, on a petrol engine using a cheap OBD tool its giving me P0420 codes (inefficient cat?) i was able to have a look at the 02 sensor voltage and it seems to jump around a lot from 0.05v to 0.8v ish even when the engine is idling when driving if you take your foot off the accellerator it drops to 0v, but over a period of say a second when crusing it show big step jumps say 0.1v to 0.4 to 0.9v etc so im wondering if this is normal behaviour for an O2 sensor.

In my experience, O2 sensors are usually quite sensitive so if there was a problem with the sensor itself or the gas it reads, you would get an error that pointed directly at the O2 sensor itself (eg. P0130) but see what others say.