Thanks guys. Dennis good video...after some google reading, some sites recommend replacing all 4 sensors at the same time...
I never suggest 'replacing all' of the O2 sensors on a vehicle - unless I know for sure that one (or both) bank(s) have been contaminated (like with a Coolant leak) and need it ...
When the 'code' was read what was the cause
It should have set a given Code(s) that will point you to the Sensor or Bank of the system that is causing the CEL to come on.
If it just the rear sensor, then it could be telling you that the 'Cat' is failing/contaminated and pointing to a future issue.
If it a given 'Bank' (Bank #1 is the 'Odd' cylinders - #2 is the 'Even') then it may be pointing to another issue - or just a failed sensor.
For the most part, you will find the 'front' sensors are often 'Non-Heated' type, while the 'rear' are 'Heated' - that is to level the response for the rear ones that are farther away from the exhaust gasses and take longer to get to their proper temp. for correct hysteresis output.
You can also read that as - fronts are often cheaper than rears, and have less wiring ...
I always try to find a Bosch replacement units if possible.
They seem to be the most forgiving and best at responding to the range the ECM is looking for and prevent more issues with the CEL lighting right after the service work.
Also, make sure you hard wire the sensor to the existing system using the proper crimp(s) and shrink-wrap over the connection. Some of the supplied 'wizz-bang'
connectors supplied with replacement sensors can lead to problems shortly after the repair if they are not carefully installed and weatherproofed ...
As fare as getting them off.
spray with penetrating oil the day before you work on it.
Then drive the vehicle just before you do the work to heat the system - as soon as you get to the sensor (still warm) touch a candle (the reason there is a box of 'Birthday Candles' in my tool box, really) to the base where the threads are. Let the candle melt into the thread area and then allow the area to cool to the touch.
Using the correct socket/wrench the sensor should now come right out - with a little force ...
You can get the correct socket(s) at many auto parts stores and HFT.
And - ALWAYS
coat the replacement sensor threads with 'anti-seize' before installing.
Make sure you keep it just on the threads - and - if you can't find the graphite/nickle based type be very careful to keep any of the standard copper type off of the sensor areas!
You can find little capsules of the correct type at AutoZoned and other chain stores - it is MUCH cheaper than buying the 'Sensor-Safe' type - like the $45 can I have from GM ...
... One after the Cat tells the one before the Cat to adjust fuel or something like that. ...
Well ... not exactly, but we'll let it go for the purposes of this thread - and to prevent a w-a-y long reply