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Discussion Starter #1
I have an ongoing issue with a 420 code, I hooked my scanner and did an 02 test and the number 2 was not sending any data, does that mean that I need to replace it or possibly something else?


thank u
 

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It's more likely your scanner isn't properly reading PIDs. A P0420 is a catalyst efficiency problem - there are other codes for O2S2 failures.
 

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I don't know what kind of test your scanner did. However, if it can read live data, check the date for front and back O2 sensors and see if the back one has a voltage, and how much it's changing.


Back sensor should provide a pretty steady voltage, maybe 0.5V, while front sensor bounces around.


Either back sensor has a problem, or the cat isn't doing its job.
 

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Discussion Starter #4
Im using an actron scanner, the car runs fine, the first 02 sensor gives a reading but the second shows no reading, where should I start?


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Discussion Starter #6
it says no reading for sensor 2, how good of a scanner do I need, how about some help instead of an insult
 

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Is P0420 the only code stored?


If the sensor was disconnected, there would be other codes set, including for the sensor heating element. And P0420 shouldn't be set, because how can the system know?



When you get the "no reading", are you in live data mode? Assuming your scanner has one.
 

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it says no reading for sensor 2, how good of a scanner do I need, how about some help instead of an insult
It's not "good" or "bad" - not all OBDII readers can read all PIDs on all cars. You need one that can read all you car's PIDs. The recommendation here is probably going to be get a Tech 2, it's guaranteed to work. Short of that, you're probably going to need to go some googling, read some product pages, contact some manufacturers... or run some trial and error at your local O'Reillys. OBDii scanners are updated all the time - what worked last year may not work this year, and vice versa. You're going to need to consult current documentation, or reach out to a manufacturer or retail outlet and get some advice. My experience is that this is a $150+ problem, but my experience is four years old and not worth much.
 

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Discussion Starter #9
would a good 02 sensor show no reading whatsoever? im using an actron scanner and im doing the o2 monitor test


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Discussion Starter #10
02 sensor myth if its gray throw it away, if its black put it back, pulled upstream 02 sensor and it is gray,,,,any thoughs?
 

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You keep asking the same question... The second O2 sensor will always show both a 0-1v signal and a 300-2000ma heater current. If it doesn't, you'll get a check engine light for it. Since you don't have that check engine light, chances are the sensor is working and your scanner just can't read it. That doesn't mean the sensor is working properly, but "no signal" (as opposed to "wrong signal") will trip an immediate check engine light.

The only way to know if an O2 sensor is working is to read it with a code reader or a multimeter (or, I suppose, an oscilloscope). While the color of the tip may indicate some type of contamination that would prevent it from working, that's not any sort of reliable test. A perfectly normal looking O2 sensor can fail internally. You can electrically examine a sensor and say "Hey, no signal" and then remove it and find that it's white and died from coolant contamination, you can't go the other way.
 

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I don't have an Actron unit, and I don't know what its "O2 sensor test" involves. It doesn't sound like it's simple live data. And it's apparently not working.



When I go to live data on my older ODB II scanner, it shows voltages reported by O2 sensors. You need to look at the O2 sensor voltages reported by the ECU, in live data mode.


As another question, was the car ever tuned? Is the catalyst the stock one? It's possible that if the car is tuned, someone turned off the O2 sensor via software.
 

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As above, the only way to know if an O2 sensor is working is to read it with a code reader or a multimeter (or, I suppose, an oscilloscope). While the color of the tip may indicate some type of contamination that would prevent it from working, that's not any sort of reliable test. A perfectly normal looking O2 sensor can fail internally. You can electrically examine a sensor and say "Hey, no signal" and then remove it and find that it's white and died from coolant contamination, you can't go the other way.
 

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can you please describe how test it with a multimeter....

thank u
Using the ammeter function, be sure there is somewhere between 300ma and 2000ma passing across either of the heater wires, and using the DC voltmeter function be sure there is voltage between 0 and 1v on the signal wire. Usually there will be between 500mv and 700mv but it will vary from car to car and manufacturer to manufacturer. Operating slightly outside this range suggests a cat problem, way outside that range (like 100mv) could be a bad sensor. Post cat O2 sensors rarely have issues.
 
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