Hi guys;
I have a question;
I need to change the O2 sensor for my Grand Cherokee 2000 4.0; it's the pre-cat sensor (NGK Oxygen (O2) Sensor Part Number 23122 ).

I think I can do the change (I'm kind of weekend warrior); however in the instructions there is a section that I don't get it and hope somebody knows;

Copy from instructions:
"
4. Install all sensors with new gasket supplied & torque to proper specs as below:
M18 sensors - Install finger tight then 1/2 - 3/4 turn with wrench / O2 sensor socket 26-33ft. lbs.
M12 sensors - Install finger tight then 3/4 - 1 turn with wrench / O2 sensor socket 13.2-17ft. lbs."

How do I know or where I can find which sensor is the one I have; it is a M18 sensor or M12 sensor; there is a difference in the torque to apply.

thanks guys;

 

I've installed quite a few O2 Sensors and have never used a torque wrench to put them in... the levels their talking about are not alot of torque

make sure the steel compression ring is on the sensor, and spin it in by hand till its snug, then give it the 3/4 -1 turn to compress the gasket... plugger in!

 

Thanks CrazyWJ242. I understand now... Well I will do it that way but first I have to get the old one out; that thing is really hard to get out; looks like somebody did welding on that O2; I'm afraid I can damage it and unable to get it out.. Let you know my results ...

 

I did it. I was able to get the O2 sensor; the O2 was stuck really tight... But after using penetrating lube (Gunk Liquid Wrench Super Penetrant); heating it up with a torch for almost 10 minutes; I was able to start moving it. I did apply torque in the tightening direction; just a little bit.
It was hard but possible; I saw the new sensor came with anti-seize on the threads and hope it will last as long as the old one (I think mine was still the original... )

 

i'v gone though 1 pair already...up/dwn stream..whats causes them to fail.its giving me a check eng. light again..dwn stream faulty

 

Make sure when you replace them to not use Bosch o2 sensors, they don't read fast enough and will start doing great things with the air/ fuel mix before they decide to die.
The NGK's are available from the dealership if you can't find them cheaper somewhere else.

 

I have used the Bosch universal splice-in O2 Sensors in 4 different vehicles. Never had a problem with any of them

 

Sometimes you get lucky, for some reason the Bosch sensors dont 'seem to last long in the Jeeps. It's been a long running complaint that the only ones that don't seem to cause problems are the factory spec NGK's.