Me and a close family friend are going to replace the 02 sensors in my car. What we need to know is where the 02 Sensors are, and how many of them there are. Sometimes I have heard that there are three, or maybe four? If anyone can help me, maybe show me a diagram.. that would be great. Thanks for all of your help.

don't have a diagram but you have 4, one one each header (I believe just after all the pipes come together), and one just after the cats. I know the ones by the cats are really easy, the others I'm not too sure about.

Jibi it correct. One each side before the cats where the exhaust comse down from the engine, and one each side after the cats.

Jibi it correct.


whoo hooo I got one!!! :D

OBD I cars have 2, before the header. OBD II cars have 4. 93-mid 95 has only 2.

Is everybody positive that there are four O2 Sensors in the 1997 model? It is extremly important to find this information out. And is it usually just one 02 sensor that would make sense to replace? Or is it just worth it to replace all four, or two?

Can anyone tell me what OBD means and such? Thanks

Is everybody positive that there are four O2 Sensors in the 1997 model? It is extremly important to find this information out. And is it usually just one 02 sensor that would make sense to replace? Or is it just worth it to replace all four, or two?

Can anyone tell me what OBD means and such? Thanks


On Board Diagnostic. It's an engine control / emissions control standard. Cars 1996 and later were mandated by law to employ OBD - II, an "upgrade" over the previous standard.

Is everybody positive that there are four O2 Sensors in the 1997 model? It is extremly important to find this information out. And is it usually just one 02 sensor that would make sense to replace? Or is it just worth it to replace all four, or two?

Can anyone tell me what OBD means and such? Thanks


Yes you have 4. Two before the cat (up stream) and two after the cat (down stream) Should you need to change one up stream o2 sensor, it makes good sense to change them both. They ought to be changed out every 80k.

Well, technically, the post cat sensors aren't REALLY O2 Sensors. They are there to verify the catalytic system has not been tampered with.

don't confuse the guy! :rolleyes: Yes, your '97 has 4 O2 sensors! :cool:

I'm not trying to, but if he gets FOUR O2 sensors and replaces the rears with O2 sensors, the car won't run right.

Honestly dude, I just bought all four 02 sensors, and now i look like the moron. Thanks a lot for everyone else who really HELPED me. You really should have said that before hand when I asked the first time instead of just saying yes you have 4 o2 sensors. Now I look like the dick.

whoo hooo I got one!!! :D

That's a first!:p

Now I look like the dick.

Not really only Human!!! everyone makes mistakes.. Even Dave!!

Honestly dude, I just bought all four 02 sensors, and now i look like the moron. Thanks a lot for everyone else who really HELPED me. You really should have said that before hand when I asked the first time instead of just saying yes you have 4 o2 sensors. Now I look like the dick.


No you don't look ike a Dick. Do all of the O2 sensors have the same part number? If you had gotten them at a reputable parts store, they should have your car's info on the computer and given you the two for before the cat and the 2 after the cat.

Note: http://www.rockauto.com/catalog/x,carcode,1188569,parttype,5132

Upstreamand downstream are BOTH listed as Oxygen sensors.

I'm not trying to, but if he gets FOUR O2 sensors and replaces the rears with O2 sensors, the car won't run right.

True if he puts in two oxygen sensors that are for the front. Not two oxygen sensors that are meant for the rear.


taken from: http://www.corner-carvers.com/wiki/index.php?OBDII%20and%20O2%20Sensors%20Explained

"The difference in front to rear O2's is explained by the way the cats work. The front O2's operation is verified exactly as described above. The rear O2's have different operational parameters because of the catalyst. During normal closed loop operation, high efficiency cats have an oxygen storage capacity. Because of this, the rear O2's will switch at a much slower rate than the front units. As a catalyst deteriorates, the oxygen storage capacity will diminsh and the switching frequency of the rear O2's will increase and begin to closely match that of the front O2's. Once that ratio of front to rear switching frequency passes a certain threshold the computer thinks the CAT is not effective and trips the MIL."

they are tech called "cat moniters" behind the catsand they are used to see if the cats are failing, ford reflashes pcm's all of the time to broaden the tolerances for the cat's but all they will do is trip a light everything will run fine
the same as torque said but easier to follow
rember the k.i.s.s. rule
Keep It Simple Stupid
i live by this rule at work

they are tech called "cat moniters" behind the catsand they are used to see if the cats are failing, ford reflashes pcm's all of the time to broaden the tolerances for the cat's but all they will do is trip a light everything will run the same


And if yiou are in an emmisions area, you will fail because you have a MIL/ trouble code.

http://www.mileliminators.com/

no emissions here so ram out them cats ang get them mil eliminators but im too lazy and poor so i leave the stock 126k exhaust alone

Honestly dude, I just bought all four 02 sensors, and now i look like the moron. Thanks a lot for everyone else who really HELPED me. You really should have said that before hand when I asked the first time instead of just saying yes you have 4 o2 sensors. Now I look like the dick.

Or I can really help you look like a dick.;) j/k

I posted this the other day so a search on the LVC may have revealed this info to you in a timely manner.....

On the Corral there is a guy selling them for $70.00 shipped for a set of 4.
http://www.corral.net/forums/showthread.php?t=809019

Just got mine today. Bought 2 sets. That is why there are 8 shown. Haven't installed them yet but I now he has only 8 sets left. I just bought another set for my Expedition a couple of minutes ago.

Again, I haven't installed them yet so performance (or even if they work for that matter) is an unknown.

i forgot to say this eariler the o2's have the green plugs and the moniters have the blue

Upstreamand downstream are BOTH listed as Oxygen sensors.

that was my point, you go to the parts store and tell them you need O2's they'll just ask before or after the cat, they categorize both under O2's

On the Corral there is a guy selling them for $70.00 shipped for a set of 4.
http://www.corral.net/forums/showthread.php?t=809019

I wonder if that was the same guy Chris was talking about way back when :confused: I don't need them now because of the aftermarket exhaust but it would have been helpful!