Just recently, I have been getting really bad gas mileage, 12mpg. I decided to change the o2 sensor but I couldn't get it out. I forgot to plug the thing back in and when I stated it up with it unplugged, the SES light didn't come on. Is this a problem? If so, what should I look into? Also, any tips on getting the damn o2 sensor out?

 

o2 sensor wont set a code unplugged like that unless you drive or run the motor long enough that the ecm knows it should be seeing some activity (voltage) on the o2 signal wire but is getting none. unless you did drive a while and it set no code-perhaps then you have a problem. WD-40 and try tightening it a c hair first before loosening. 7/8 deep six point socket. also helps if the manifold is hot-use gloves

 

Ah, I completely forgot about o2 and closed loop. Thanks for the tip on getting the thing out.

 

I just tired driving my car without the o2 sensor plugged in and I still don't get a SES light. My light does work because it comes on when my ignition switch is on. What could be my problem?

 

Hmmn, somone else posted about this before as well, ran around with it disconnected for who knows how long. Never set a code. Don't recall reading if there was ever an answer, but I do know that when I was working on my car a few years ago for a MAF problem, I disconnected the O2 sensor and set a code immediately.

Don't recall is the temp was warm or not...most likely the engine hadn't been run long when I disconnected it, I don't like getting burned on hot parts

 

7/8ths deep socket, 1/2 drive...12 inch extension...your ratchet will stick out in front of the manifold enough to get good leverage on it.

Do it when the exhaust is warm.

Don't over tighten the new one whaen you install it.

 

Is something not functioning properly for my light not to come on?
I think JETHROIROC had a problem like this but he hasn't posted lately.

 

Try unplugging the TPS connector and see if you store a code.

As far as whether t's working correctly or not, I can't say for sure either way...could be an issue with the EPROM for different years/combos? Not sure.

 

Not to be a smartass but maybe your bulb is blown or the contacts are bad?

 

I have the same problem when unplugging the O2 sensor it will not set a code. The car will be in closed loop and I unplugg the sensor and drive around and no code will come up. I know the ECM is working properly as I have scanned it with my scanner and all is okay.

 

I've been fighting some O2 problems and ran my car for about 100 miles with the sensor unplugged before it threw a code. I think I may have been picking up some stray voltage from my plug wires since the autoxray was still reporting 400mv from the O2 sensor with the thing unplugged!

 

the engine mgmt. system found in our f-bodys, and most computer controlled systems used by other manufacturers that use a zirconium o2 sensor, when scanned for data, and when checked with a dvm also, will always show 400-450 millivolts on the scantool o2 data when the sensor is disconnected. the voltage is there because the ecm is waiting for the o2 sensor to output that same voltage the first "crosscount" which signals the computer that the o2 sensor is ready for closed loop operation and the ecm will close loop if all the other required parameters-coolant temp, all sensors are functional, etc are proved out as good. its a normal thing to see-now a titania o2 sensor is a whole nuther story we will skip it fer now:hail: