I was wondering if I disconnect the O2 sensor shouldn't the check engine light come on? I am still trouble shooting my engine here and so far no one can help me because I get no check engine light. I disconnected the coolant temperature sensor and i got the light I hooked it back up turned off engine restarted it and light went off. I disconnected the O2 sensor and nothing happened i even let it run for a while and nothing seems to run fine without it. I am seeing if running without it connected will solve the problem if so then I will get a new one to replace it. I can't afford to replace all sensors or I would so I figure this is the next best thing to try to find the faulty sensor.

 

I just went out and disconnected the MAP sensor got light and it ran horrible. so only sensor I have left is the O2 sensor.

 

I will give this a wack...
what problem are you chasing with all the unpluging?

Do not know why no MIL for unpluged 02....could rationalize that the time to WARM sensor up has not been met, ie still in OPEN loop, suspecting this is a 4wire sensor the heated circuit portion would soon show a code.
The reason is not important right now... and the big disclaimer not all CODES will set MIL on.... the reason I always ask for a scan. ie p0147

symptons? be specific and L O N G if necassary
vehicle stock- ?
recient work?
accidents?
do you have a scanner?
model year - engine- colour?

 

That was it. I have ran it all day with O2 sensor unplugged no issues. I had another post about 92 3.0 litre running bad I believe I called it throttle problems I changed the TPS and it ran for about 3 days fine then every day since it had problems and I had to disconnect the battery then it would run good for a few hours and id have to repeat. I never got a CK engine light no matter how bad it ran and all the places I took it to said it had to be a 96 or newer and have a CK engine light to be able to get any codes. I was at a lose so I just started trying to weed out sensors without spending a ton and change them all. when I disconnected either the map sensor or the coolant temp sensor I got CK engine light. when I did MAP it ran like I would expect it too with it disconnected. I disconnected the O2 sensor no CK engine but also no more driving issues. I only have one concern and that is today it was about 82 out and the last few weeks it has been between 90 and 100 out so I thought that maybe the computer was overheating. I will just have to wait till it gets hot outside again to be positive it wasnt that but for now I am happy it is running good again.

 

i put new O2 sensor in and so far it runs like a champ. So funny that I got no ck engine light with a bad O2 sensor. Computers for ya I always thought they were more of a problem then any good and again it has proved me right.

 

Just information, an o2 sensor fault will only cause the ck engine to flash on and off. Unless you have a shorted curcuit. You should have had a stored code.