How do you tell if your O2 sensor is bad?

[ETalon95]

How do you tell which O2 sensor is bad... and where is teh one behind the cat located and the one before the cat. and how hard is it to replace?

 

[ddavisaf]

CEL will show if O2 is bad usually. You will run rich at idle if it's bad. first o2 is located on the "o2 housing" convient huh? The second is located just behind the cat, it's the ONLY plug goign into the exhaust. They're not hard to change.

 

[QuienesTuPapa]

Usually you'll get a CEL if an o2 sensor is bad. If you dont have problems running rich then most likely it should be fine. If you're going to replace it, it might be a good idea to go to an auto parts store and buy an o2 sensor socket, they really help out. Also, get a can of PB blaster and soak the hell out of it the night before. Give it a couple blasts before you actually do the work too. They can be a huuuuuge pain to get out, i know mine were.

 

[VBGSX]

CEL will show if O2 is bad usually. You will run rich at idle if it's bad. first o2 is located on the "o2 housing" convient huh? The second is located just behind the cat, it's the ONLY plug goign into the exhaust. They're not hard to change.

Usually you'll get a CEL if an o2 sensor is bad. If you dont have problems running rich then most likely it should be fine. If you're going to replace it, it might be a good idea to go to an auto parts store and buy an o2 sensor socket, they really help out. Also, get a can of PB blaster and soak the hell out of it the night before. Give it a couple blasts before you actually do the work too. They can be a huuuuuge pain to get out, i know mine were.

The key word in both of these posts is "usually". It will not always throw a CEL.
Combine the answers in both the above posts and you have your questios answered.
Summary:
Where are they located:
1. O2 housing(Look straight down next to your turbo and find the O2 housing. You can't miss it sticking out.
2. Just behind the cat.

What makes the job easier:
1. PB Blaster(definitely. Good recommendation)
2. O2 socket
3. Probably a breaker bar. Mine were in there pretty good even after PB Blaster

If you have a multimeter and know how to use it, let me know.
I'll tell you how to check the O2 sensor.
Also, if you have a logger or a friend with a logger, you can trouble shoot if you have a bad O2 sensor or which one is bad.

Good luck

 

[ETalon95]

well the CEL is on and it reads P1400 and smoke pours out of my exahust and my car idles terribly and it smells really bad during idle. i just dotn knwo which sensor replace bc they arent that cheap and i dotn wanna replace teh wrong one.

 

[VBGSX]

The front one is the one the ECU uses in closed loop mode(idle, partial throttle).
The one past the cat is more for emissions checking.

The front one

 

[ddavisaf]

Replace the O2 sensor directly below the exhaust manifold. You will see it poping out of the exhaust. Next time make sure you post all CEL's and symptoms when faced with a problem. It will help us pin point the problem instead of having to guess what it might be. You should only have to replace the first O2. If CEL doesn't go away you can replace the second in line.

 

[ETalon95]

Can I replace the O2 sensor when the car is hot or will I crack the O2 housing?

 

[flinguist]

The key word in both of these posts is "usually". It will not always throw a CEL.
Combine the answers in both the above posts and you have your questios answered.
Summary:
Where are they located:
1. O2 housing(Look straight down next to your turbo and find the O2 housing. You can't miss it sticking out.
2. Just behind the cat.

What makes the job easier:
1. PB Blaster(definitely. Good recommendation)
2. O2 socket
3. Probably a breaker bar. Mine were in there pretty good even after PB Blaster

If you have a multimeter and know how to use it, let me know.
I'll tell you how to check the O2 sensor.
Also, if you have a logger or a friend with a logger, you can trouble shoot if you have a bad O2 sensor or which one is bad.

Good luck

How do you check your O2 sensor with a multimeter?

 

[xveganxcowboyx]

How do you check your O2 sensor with a multimeter?

You probe it for voltage. Should be under 1 volt and should change with throttle. DSM's have 4 wire O2 sensors. The 2 white wires are to heat the sensor. You probe one of the others, can't remember which one at the moment.

The hayne's manual I think talks about another method at a connector, but I've only ever tested by the wire.

 

[firebirdvert305]

"old school" way of doing it....U can do it the right way and test for voltage but the way my dad told me works 9.5/10 times on all the 02 sensors we've done on our cars. Remove the 02 sensor...shake that b!tch and if u hear a "tinging" noise its bad The noise sounds like when a lightbulb burns and turns black...if u know wut i mean...it sounds exacly like that tinging noise a burnt light bulb makes when u shake it....try it if u dont believe me...its almost a proven method...and obviously if it dosent make that light bult tinging noise...its good.

 

[VBGSX]

How do you check your O2 sensor with a multimeter?

Here's all the good stuff

Proper operation of the O2 sensor depends on several things(from Haynes)
1. Electrical: make sure you have a good clean connection. Terminals shouldn't have any corrosion, etc.
2. proper operationg temps: The ECU will not react to the sensor signal until the sensor reaches approximately 600 degrees F.

To check the front O2 sensor:
1. Put the car up on jackstands
2. disconect the O2 sensor plug
3. measure the resistance between the heater terminals of the sensor connector. There should be continuity. If not, replace the sensor
4. Locate the output terminals of the oxygen sensor. Connect the multimeter to the terminals
5. With the O2 sensor plugged in, start the engine and warm it up to normal temps. Check the O2 sensor signal voltage.
The voltage should range from 100-900 millivolts(0.1-1.0 volt) and switch actively between high and low readings.
6. If everything is working properly, go to the ECU check from the ECU to the O2 sensor plug to make sure there are no breaks in the wire.

Just for fun:
If you ever wanted to see how your running in(open loop) WOT.
Connect a multimeter to the sensor. 0.1 volt=lean 1.0=rich.