can someone help explain what I'm looking at - Scanner Question

[kctyphoon]

So I just picked up the HF branded autel scanner that does abs the other night. I started watching some videos people suggested,, and a lot more on YouTube to learn what I can by myself. I obviously can't tackle it all at once, so I'm starting with learning how to understand the live feed from the O2 sensors, and it seems the P0420 code is a popular one for those. (Cat below threshold)

Anyway, all the videos I've watched only had 2 O2 sensors to monitor, one pre and one post cat - and all the values displayed were in volts.. The scanner I bought is showing the values from (taking an educated guess here) BOTH upstream O2 sensors in milli amps (ma) instead of volts. I can't change the value, so I have to assume this is normal. I'm scanning a 2012 Honda Crosstour V6 (3.5?). Just bought the car about 2 months ago, so there's a lot I don't know about the drivetrain still.. it has no issues, so it's my Guinea pig to learn the tool.. Meanwhile, BOTH downstream O2 sensors are in volts.. They both hang around .6 and don't move much so they have to both be downstream so since there's 2 cats, and both are working..


I'll post a picture of the values (remember they were changing, so take that into consideration when looking at the pic. They are what the WERE for only a second)


So here's my questions -

(1) - why is this like that

(2)-if these ARE both upstream O2's that are showing values in (ma), and not (v), then what are the numbers/behavior I'm keeping an eye out for if there was an issue with them - since normally in (v) it seems they should rapidly switch from high to low between 0 and 1 volt , while the rear should stay smooth and even hovering around 0.5v.. Is there a hi/low in (ma) I should watch for


(3)- if a cat was bad, the upstream and downstream value in volts would be almost the same - how do I determine they are the similar if the values are being given in forms?

(4)- IF a rear O2 sensor was bad, and the CAT was good, what reading/difference would I see in that rear O2 - (considering the wiring was ok) -- would it hover more towards 0v, more towards 1, would the value be erratic, or could it be either?

These pictures are after a 15 minute drive, most on the highway. Pulled over into a parking lot to play with the scanner, so car was nice and warmed up..

(Ignore duplicate O2 in this pic, was playing with the custom menu)

 

[GTA Matt]

You mean interpreting scan data isn't as easy as it looks on youtube?!?! Who woulda guessed!

Front has A/F sensors, not o2 sensors. Their value really doesn't change a whole lot compared to an o2 sensor and obviously reads in mA.

Can't really tell too much which way an o2 is biased by numbers. Really need the ability to graph the data. o2's (and A/F sensors) can fail in multiple ways. Heaters can fail, voltage can stick high, low, switch lazy, signal voltage can short to heater ground or heater B+. Fuel trims play an important roll as well. Simply viewing o2 data really doesn't tell you a lot.

 

[redwrench60]

I thought you fixed that Honda with a $35 sensor after calling all mechanics thieves for recommending a cat converter for a P0420 code.

 

[Badattitude]

You mean interpreting scan data isn't as easy as it looks on youtube?!?! Who woulda guessed!

Front has A/F sensors, not o2 sensors. Their value really doesn't change a whole lot compared to an o2 sensor and obviously reads in mA.

Can't really tell too much which way an o2 is biased by numbers. Really need the ability to graph the data. o2's (and A/F sensors) can fail in multiple ways. Heaters can fail, voltage can stick high, low, switch lazy, signal voltage can short to heater ground or heater B+. Fuel trims play an important roll as well. With the exception of cross count frequency and KOEO voltage Simply viewing o2 data really doesn't tell you a lot.

.....

 

[Ramblin Man]

I'm not familiar with your scanner, my scanners are snap on. But, IF your scanner has an enhanced side(manufacturer specific), and a global(generic side) side, you can switch over to the global side and see your upstream sensors in a voltage format. A lot of times anyway. I hope that works and helps you.

Also, if your scanner will graph data, and let you select just certain PIDS, that will help diagnosing.

 

[kctyphoon]

I thought you fixed that Honda with a $35 sensor after calling all mechanics thieves for recommending a cat converter for a P0420 code.

The car is fixed smart *** - but reading about it and surfing YouTube, it's a popular code and one I'm kinda familiar with now - so it seemed like a logical starting point to learn about the scanner I just bought - Don't ya think?? This ISNT the same car I'm using.

But while you on the subject, maybe you'd like to tell everyone how many ELD's are in a 2002 civic, and then defend the place that told my mother "oh there's 2 in the car, another one in the same spot - the price we gave you was to replace that one, not the one your son changed".. (Cause I didn't clear the code after replacing the part)

Don't blame me for calling people dishonest - I didn't give them that rep - they earned it. But don't worry - next time a storm blows though and your without power, maybe I can swing by and ask ya how long it's gonna take ya to put a few poles in on your own and see how ya do.

 

[blown94conv]

Call the tech support line.

 

[redwrench60]

The car is fixed smart *** - but reading about it and surfing YouTube it's a popular code and one I'm kinda familiar with now - so it seemed like a logical starting point to learn about the tool. This ISNT the same car I'm using.

I don't know about the rest of the Mechanics on this forum but I get tired of being lumped in with thieves and crooks in one thread then asked for help in another. Good luck with your ride.

 

[logikal]

Agree with above, and Im not usually one to jump the in on this. First you need to understand how an o2 sensor functions. Your talking about narrowband sensors that the "youtube mechanics" are showing you. they only have three steps in there correction, stochiometric, lean, rich. what your seeing is a wideband, setup that actually reads lambda (the difference in air and fuel {its a ratio....}) which is utterly useless dependent on cat temp, engine temp, management.........srry dude but you need to actually learn what the hell an O2 is before thinking this is simple.

Heres some reading to help....http://www.bosch-lambdasonde.de/en/downloads.htm

that is just the BASICS outlined in those PDFs. But a good starting point nonetheless.

 

[kctyphoon]

I can graph data on this scanner - but I can't set the parameters .. So if I try to graph the O2's voltage, the graph is very fast. I can get the basic idea that the voltage is going up/down fast, and tell what values its staying within - but it's not like a professional tool.. It's easier to just watch the actual numbers and not use the graph ( so far).. Remember I just got the thing, so it's a learning experience.

 

[kctyphoon]

I don't know about the rest of the Mechanics on this forum but I get tired of being lumped in with thieves and crooks in one thread then asked for help in another. Good luck with your ride.

Don't remember ever "lumping" anyone else into anything.. I named the shop in the thread your talking about.. If you had a bad day, by all means - feel free to take a nap.

 

[kctyphoon]

Agree with above, and Im not usually one to jump the in on this. First you need to understand how an o2 sensor functions. Your talking about narrowband sensors that the "youtube mechanics" are showing you. they only have three steps in there correction, stochiometric, lean, rich. what your seeing is a wideband, setup that actually reads lambda (the difference in air and fuel {its a ratio....}) which is utterly useless dependent on cat temp, engine temp, management.........srry dude but you need to actually learn what the hell an O2 is before thinking this is simple.

Heres some reading to help....http://www.bosch-lambdasonde.de/en/downloads.htm

that is just the BASICS outlined in those PDFs. But a good starting point nonetheless.

Can't get them to download from this tablet.. I'll look at it on my desktop later tonite... But knowing the front sensor aren't O2's at least give me the next thing to look into, and explains why it's not being read in volts. . I'm not trying to do everything a professional scanner can - just get some more direction over pulling a code.

 

[goforride57]

Here's my reply to the original question. Yes.

 

[Hondarancher4435]

There's many great mechanics out there but there's also many making a bad name for the repair industry

 

[Rlfd213]

Unless I read this wrong there is voltage readings for both O2 banks towards the top of the screen.

 

[Badattitude]

Unless I read this wrong there is voltage readings for both O2 banks towards the top of the screen.

Those are for post cat sensors not pre cat ie: O2B1S2 & O2B2S2

 

[jerseykat1]

When diagnosing a/f ratio sensors your best bet is to look for anomalies in the graph. You can perform some tests to get a better understanding by introducing some unmetered fuel (carb cleaner) and watching your ratio sensors on the graph. This is also a quick way to test your upstream sensors. Create vacum leak see if they react similarly on the graph then richen with carb cleaner and see if they react similarly in the opposite direction.

Better indicator of what's going on is to watch fuel trims.

Sent from my Nexus 6P using Tapatalk

 

[kctyphoon]

Yes both ending in s2 is the downstream.. Bank1 sensor2 / bank2 sensor2..

I kinda got the answer I needed (for now) though - that the pre-cat sensors are A/F and not O2... So I'll just need to get a basic idea about the info the readings mean for those.. But thanks for the guys that helped.. Both the car and scanner are new to me, so there's a learning curve here..

 

[Ponchoguy]

The car is fixed smart *** - but reading about it and surfing YouTube, it's a popular code and one I'm kinda familiar with now - so it seemed like a logical starting point to learn about the scanner I just bought - Don't ya think?? This ISNT the same car I'm using.

But while you on the subject, maybe you'd like to tell everyone how many ELD's are in a 2002 civic, and then defend the place that told my mother "oh there's 2 in the car, another one in the same spot - the price we gave you was to replace that one, not the one your son changed".. (Cause I didn't clear the code after replacing the part)

Don't blame me for calling people dishonest - I didn't give them that rep - they earned it. But don't worry - next time a storm blows though and your without power, maybe I can swing by and ask ya how long it's gonna take ya to put a few poles in on your own and see how ya do.

Your next step is to follow the diagnostic trouble tree for that vehicle for the P0420 code and go in order with all of the tests and such to determine why the P0420 is present.

You can get that either in the OEM shop manual or a Mitchell/Alldata subscription. A lot of things can cause a P0420 code and you have to in order or you might change parts that don't need to be changed.

 

[kctyphoon]

When diagnosing a/f ratio sensors your best bet is to look for anomalies in the graph. You can perform some tests to get a better understanding by introducing some unmetered fuel (carb cleaner) and watching your ratio sensors on the graph. This is also a quick way to test your upstream sensors. Create vacum leak see if they react similarly on the graph then richen with carb cleaner and see if they react similarly in the opposite direction.

Better indicator of what's going on is to watch fuel trims.

Sent from my Nexus 6P using Tapatalk

I'm guessing this is (kinda) the equivalent of introducing propane to see how the O2's react?

 

[jerseykat1]

Most cars are A/F sensors now.

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[GTA Matt]

When diagnosing a/f ratio sensors your best bet is to look for anomalies in the graph. You can perform some tests to get a better understanding by introducing some unmetered fuel (carb cleaner) and watching your ratio sensors on the graph. This is also a quick way to test your upstream sensors. Create vacum leak see if they react similarly on the graph then richen with carb cleaner and see if they react similarly in the opposite direction.

Better indicator of what's going on is to watch fuel trims.

Sent from my Nexus 6P using Tapatalk

You can monitor the sensors range from the drivers seat (with maf and vacuum booster systems). Pump the brake pedal quickly about a dozen times until the fuel trims max, then let off. o2's will go lean while pumping, then jump full rich when you stop.

Thats all for this weeks tech tips....

 

[kctyphoon]

Your next step is to follow the diagnostic trouble tree for that vehicle for the P0420 code and go in order with all of the tests and such to determine why the P0420 is present.

You can get that either in the OEM shop manual or a Mitchell/Alldata subscription.

Yea so far that car (my mothers 02 civic) hasn't had another light come on.. It's been (3? 3&1/2?) weeks now.. I've read all sorts of things from people needing to change plugs/wires/rotor - to the downstream O2 to get the code off their (older) accord or civic. I'm really not chasing any trouble down. Maybe that car just misfired once or twice and it just tripped the code. Who knows. Maybe it'll come back in a month or two, maybe it never will.

I'm just here (now) cause since I spent a little time looking into that code - I'm a little familiar with it, and figured it made sense to use the info to help figure out some features on the new scanner.. I went from planning on spending $20 to over $100 in a few hours once I stared to see what a little extra $$ gets you.(and HF had a 25% off coupon good to the next day) If I use it once it'll probably earn its money back. If I never so, I've wasted a lot more money on a lot less things. The info it's displaying is from a '12 crosstour.. There's nothing wrong with it, so it's a good time to see what values come up.

 

[jerseykat1]

You can monitor the sensors range from the drivers seat (with maf and vacuum booster systems). Pump the brake pedal quickly about a dozen times until the fuel trims max, then let off. o2's will go lean while pumping, then jump full rich when you stop.

Thats all for this weeks tech tips....

That's an awesome tip!

Sent from my Nexus 6P using Tapatalk

 

[Atthelastminute]

I haven't really seen an explanation of the mA vs V so far. A/F sensors pump oxygen to compensate for the rich/lean condition of the exhaust. The PCM measures the amps required to equalize and changes fuel trims to compensate.

Honda uses the secondary sensors to detemine fuel trims, and the primary sensors to fine tune based on the results. Most manufacturers don't reveal their programming for A/F sensors still.


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[kctyphoon]

I haven't really seen an explanation of the mA vs V so far. A/F sensors pump oxygen to compensate for the rich/lean condition of the exhaust. The PCM measures the amps required to equalize and changes fuel trims to compensate.

Honda uses the secondary sensors to detemine fuel trims, and the primary sensors to fine tune based on the results. Most manufacturers don't reveal their programming for A/F sensors still.


Sent from my iPhone using Tapatalk

Thanks for that. That's was a good explanation. First post since 2013 - I'm honored. Lol. I might try to get a Bluetooth scanner to use with one of my tablets later. So far the graphing isn't tereffic on the one I bought but it still does a lot for someone like me. Thanks again