What Conditions Need be met Before Oxygen Sensor Comes into Play?

[M80]

I was suffering poor consumption, so monitoring the oxygen sensor, and other possible causes.
I replaced it last week and yesterday consumption was as good as ever.

But I noticed that on cold start the the voltage is at 4.8 volts and O2 at 1.02 for some time, and I couldn't see a common cause for when the ECU decided to bring it into play.

Coolant temp can be from as low as 40 degrees or as high as 59 before the voltage drops to 1.01 / 1.02 and O2 varies from 1.45 to 2 (when coasting).

The MAF looks to me to be functioning the same no matter.

If I switch off (short journey style) when I resume the journey, possibly within minutes, the oxygen sensor is out of play again, for possibly a mile.

 

[alexanderfoti]

The o2 sensor has a heater built in, the heater heats up the sensor until it starts working. On a petrol, this is normally 2-3 minutes. Diesel usually around the same, assuming the heater is working correctly.

 

[M80]

Thanks for that Alex.
I hadn't considered the heater even though I ran the heat / rev to 1,500 revs actuation for 3 minutes, a couple of weeks ago.

That did improve the o2 recognition but consumption was still naff. So I bought a new sensor.

I'll check next time I'm out but the recognition of the sensor by the ECU seems to take longer.

 

[supernoodle]

The O2 sensor is not used until dew point has passed, ie no chance of water droplets in the exhaust. There will be no heating or current pump active.The sensor contains ceramic, water hitting that will crack it.

As there is no direct measure of humidity, dew point is modelled based on various temps and time.