o2 sensor and closed loop

[pthoma1]

I am passing this question on from a friend: If an o2 sensor fails, could this trick the pcm into going into open loop and not setting an ses??? Or once the pcm goes into closed loop does it stay in closed loop?
Thanks Paul

 

[Hib Halverson]

I am passing this question on from a friend: If an o2 sensor fails, could this trick the pcm into going into open loop and not setting an ses???

No.

Or once the pcm goes into closed loop does it stay in closed loop?
Thanks Paul

Yes.
But....if the car has a bad O2S it might not go into closed loop and the bad O2S will set a code

 

[vettered91]

Is there some way to find out if my engine is working in open loop all the time? (with out a scanner)

I don't have cats and I know for sure the rear O2 sensor (the one after the cat) is not working but I don't get any "ses" light.

It drinks fuel like an "gashoholic"!! :cry

 

[Robertwav1]

Unplug sensor to see if engine runs different. It will run rich in open loop this way. If the sensor goes bad the wrong way it can run rich enough to allow fuel to drip from your tail pipe. Don't forget the computer is looking for an input from this thing and it will use what it gets, right or wrong. Forced open loop it just runs rich. Hope this helps!

 

[vettered91]

Robertwav1,

Thanks for the info, I'll unplug the sensor in the mornig and see what happens!