Recent Topics
Kellogg 331TV Cylinder Head
by Allan_G
5 minutes 49 seconds ago
TSC Sale through Sept. 21st
by SilverC6
8 minutes 17 seconds ago
Havoline High Mileage?
by asiancivicmaniac
12 minutes 0 seconds ago
2000 FRC Corvette
by donnyj08
30 minutes 43 seconds ago
0W-20 Question
by Mathew_Boss
41 minutes 28 seconds ago
5w30 cold pump ability
by Camprunner
Today at 08:43 PM
Mobil 1 Severe Service Test
by buster
Today at 08:43 PM
Toyo OC/CT
by used_0il
Today at 08:38 PM
Can I put ATF in my transfer case?
by StuDawg
Today at 08:02 PM
Build your "Ideal" Oil Filter
by GumbyJarvis
Today at 07:56 PM
GC 0W-30 | '10 Impreza | 4.2-5.7k mi
by Scotthew
Today at 07:47 PM
Alcohol-Based Fuels From The Early Years Of Automo
by babbittd
Today at 07:44 PM
Newest Members
waynesworld, Arcticfox, informme, Sherlock, Pokermatters
51330 Registered Users
Who's Online
84 registered (Apollo14, 29662, Allan_G, actionstan, 9 invisible), 1467 Guests and 210 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
51330 Members
64 Forums
219388 Topics
3462176 Posts

Max Online: 2862 @ 07/07/14 03:10 PM
Donate to BITOG

Topic Options
#2617533 - 05/03/12 10:02 PM Oxygen Sensor vs Air/Fuel Ratio Sensor
FusilliJerry82 Offline


Registered: 06/03/06
Posts: 779
Loc: Richboro, PA
My fathers O2 (maybe) sensor threw a code so I bought a direct fit Denso to find that the plug was not keyed correctly. Tried a CA emissions one. Not correct. So I checked Denso's catalog and they list an oxygen sensor and an "air/fuel ratio sensor" of which I've never heard the terminology. The listing for the A/F ratio sensor is keyed correctly but what throws me is that for the same car, a 2003 Camry 2.4L, they list BOTH an O2 and A/F ratio sensor for upstream. Can anyone chime in on this? Does this car have in effect, three O2 sensors or is it that some models have one or the other?
_________________________
2000 Protege 1.6 215k - Mopar Max Pro 10w-30/Mopar Oil Filter

Top
#2617575 - 05/03/12 10:42 PM Re: Oxygen Sensor vs Air/Fuel Ratio Sensor [Re: FusilliJerry82]
Scott_Tucker Offline


Registered: 12/31/09
Posts: 854
Loc: Santa Cruz, Ca.
In a nutshell, the A/F ratio sensor is more accurate than an O2 sensor. They use the A/F sensor up stream because they use that to check the air/fuel ratio. The one after the cat is simply to verify the cat is working so an A/F sensor would be overkill.
_________________________
2012 Honda Civic Si, Dyno Blue Pearl

Top
#2617584 - 05/03/12 10:52 PM Re: Oxygen Sensor vs Air/Fuel Ratio Sensor [Re: FusilliJerry82]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
Yeah, if they list both an upstream O2S and an AFR for Cali emissions, the upstream O2S is probably a catalog error.

Top
#2617597 - 05/03/12 11:07 PM Re: Oxygen Sensor vs Air/Fuel Ratio Sensor [Re: FusilliJerry82]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
The AFR is a wideband O2S. Instead of having an output signal that is a voltage above/below 450mv to indicate rich/lean, a current is applied to a sort of, well, half of an O2 sensor built into it to force the main O2 sensor within the AFR to signal 450mv. The direction of current flow indicates rich/lean and the amount of current required indicates how rich/lean the mix is.

They work wia the same basic mechanism, but with an extra layer on top for the wideband/AFR sensor allowing for much greater resolution. Because the regular O2S varies voltage as a signal and the AFR uses varied current as a signal there is no way to make one work in place of the other despite the plug looking the same. File off the bumps and swap terminals around as much as you want, it can't work.

Knowing how far off the mix is from stoichiometric rather than just rich or lean allows the ECU to correct the mixture much more quickly than just moving it a hair and waiting for a response from the O2S. This also offers the engineers an option of using a mix that is "a little rich" or "a little lean" in certain operating conditions without doing the "drop to open loop and hope for the best" trick.

Top
#2618073 - 05/04/12 02:58 PM Re: Oxygen Sensor vs Air/Fuel Ratio Sensor [Re: FusilliJerry82]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
yonyon is right.
Upstream and downstream O2 sensors are often identical, just with different length leads.
Many O2 sensors are ON/OFF, but a wideband varies with theO2 readings.

Top