Difference Between Air/fuel Ratio Sensor And O2 Sensor

[ayeung74]

I need to replace my air/fuel ratio sensor (Bank1/ sensor1), but I want to make sure I get the right part because I am not sure if I have to get a specific AFRS like the DEnso part that I saw that sells for around $200. I also saw universal O2 sensors (before catalyst) that sells for alot less. Bosch sells a O2 sensors (part# 13354 and 15734-universal) , but I wasn't sure if it could be used in place of the AFRS.

What is the difference and is it essential to have a specific AFRS? I don't want to spend an extra $100 if I don't have to. I've seen lots of posts about oxygen sensors, but I haven't found info about the actual part I can use.

Can someone let me know?

[SKperformance]

there are many threads in the rx section (exact same engine) with others using other parts and one specifically with issues of a certain type, sorry don;t remember the details.

[wwest]

Two components, exactly the same, used for two different purposes.

Both are used to detect oxygen content in the exhaust gasses. First one to make sure the A/F mixture is correct, second one to be sure the catalyst is operating correctly.

[ayeung74]

Thanks SK...

[Bigrick]

I got the Bosch oxygen sensor (part # 13354) as recommended by Auto Zone for my p0135 code (bank 1 sensor 1 oxygen sensor). Is this part OK?

[ayeung74]

I got the Bosch oxygen sensor (part # 13354) as recommended by Auto Zone for my p0135 code (bank 1 sensor 1 oxygen sensor). Is this part OK?

I did a lot of reading on the forums and people have used different sensors (both AFRS and universal O2), Densos and Bosch and others (like SNK or Walker). I was reading on the forums about the differences between the two and although they both essentially do the same things, there is a subtle difference between the two.

What distinguishes AFRS from regular O2 sensors is that the AFRS is what is known as a wide range O2 sensor whereas the basic O2 sensor is a narrow range sensor. It can detect a wider range of air/fuel ratios than the basic O2 sensor. Also, the AFRS has a little bit more circuity to enable it to detect more minute variations in the exhaust system air content (more sensitive than the O2 sensor). Therefore, it is able to make better adjustments theu the ECM to add or subtract fuel to produce a better mix of air/fuel to maximize efficiency and minimize emissions.

hope that helped.

[92Lex]

Conventional O2 sensor's: above 450mv = rich, below 450mv = lean.

With a typical O2 sensor the ECM cannot tell how rich or lean a mixture actually is. All the ECM attempts to do is maintain an average sensor voltage of 450mv, to maintain a stoich a/f ratio. The lower the exhaust flow the less activity you'll see from these sensor's. They are simply not as acurate as A/F sensors.

A/F sensor's output is linear, increasing or decreasing with mixture strength in the exhaust system. These sensor's have a diffuser chamber that measure oxygen ion flow between chambers, that info is then sent to the ECM and processed as "actual oxygen content".

Operation temps and warm-up time also differ between these two sensor's.

Sensor output:

O2 Sensor - 0 to 1000mv

A/F Sensor - 0 to 5v

[Bigrick]

I am still confused. Does anybody know if my (generic?) Bosch oxygen sensor will work in my '97? Or should I buy one from Lexus? Thanks.

[ayeung74]

I am still confused. Does anybody know if my (generic?) Bosch oxygen sensor will work in my '97? Or should I buy one from Lexus? Thanks.

Bigrick--(nice, is this a euphemism?)

From what I have read on the forums and elsewhere--I also have friends that have installed Bosch sensors on the pre-cat side sensors--and they do "work". They will do the job, but based on the differences between the AFRS and a regular O2 sensor, it would probably not run as efficient. Also, there is the difference in the heater element, O2 sensors need to be heated and the AFRS needs to be heated more rapidly and to a higher temp because they need to reach operating temp quickly since they are the ones that read and detect the air/fuel mix. The rear sensors do not need to be heated as quickly and as hot and only serve to detect exhaust emissions.

So basically. you can get by with a Bosch sensor, but it would probably be better in the long run to use an AFRS than an O2 sensor. Brand is not really the issue, only the type. I know that Denso makes AFRS for the Lexus.

[Bigrick]

Thanks for the speedy reply. I called Lexus parts. Based on my vin, I have the oxygen sensor only, not the AFR/oxygen sensor. FWIW, if I can return the Bosch sensor, I will go with the Toyota brand, which is the same as the Lexus. It's $50 more than the Bosch. So maybe I'm wasting money, but I'll have more peace of mind.

By the way, "bigrick" is not a euphemism. My son is also Rick. Even though he is bigger than me, I am bigrick because I'm older.

[michaelamiller]

I have a 2001 Lexus ES300 with both the Check Engine Light and Trac Light on. AutoZone analysis showed code P1135 Air/Fuel sensor heater circuit malfunction. I replaced the oxygen sensor, Bank 1, Senor 1, by the radiator easily. That did not solve the problem. I tried to replace, Bank 1, Senor 2, between the firewall and engine, on the exhaust manifold. That sensor was frozen in place, seized, and could not be removed.

I went to the Lexus dealer initially and they wanted $ 162. for analysis, $ 214. for the part, and $ 216. for labor. I have 80,800 miles on the car.

Please tell me how you think I should proceed?

Thanks,

Michael A. Miller

[rreuth]

I have a 2001 Lexus ES300 with both the Check Engine Light and Trac Light on. AutoZone analysis showed code P1135 Air/Fuel sensor heater circuit malfunction. I replaced the oxygen sensor, Bank 1, Senor 1, by the radiator easily. That did not solve the problem. I tried to replace, Bank 1, Senor 2, between the firewall and engine, on the exhaust manifold. That sensor was frozen in place, seized, and could not be removed.

I went to the Lexus dealer initially and they wanted $ 162. for analysis, $ 214. for the part, and $ 216. for labor. I have 80,800 miles on the car.

Please tell me how you think I should proceed?

Thanks,

Michael A. Miller

There are lots of posts on this CEL coming up along with the VSC light. The code that is found (P0135) normally seems to point to the Bank 1 Sensor 1 oxygen heater circuit. But, as you note, it can be expensive and/or difficult for the DIYers to replace that sensor. I am having the same problem with a 2003 RX300 with just over 100K miles. I have cleared the codes many times, but it will return after a short time. Short time appears to be anything between 10 and 500 miles.

I did clean the MAF, checked the vacuum air line on the back of the air cleaner box, and replaced the Bank 1 Sensor 2 oxygen sensor heater, but the CEL and VSC lights return.

I cleared the code (again), and I am now using a Tier II gasoline exclusively. I have been using it for about 1000 miles (3+ tanks). The lights have not come back on. I have my fingers crossed. I don't know exactly how to explain why the Tier II gas seems to be working, but I would note that I also have a 2002 Corvette. The fuel gauge would go to zero after getting to between 1/2 and 1/4 of a tank. This would cause the low fuel warning lights to come on and force me to fill it with gas quickly (either that, or try to manage the fuel by following the odometer readings). On a Corvette forum, I came across a post noting that the problem was believed to be caused by using a non-Tier II gasoline. After awhile, the non-Tier II gas would corrode the surface of the fuel gauge sensor in the fuel tank. Using a Tier II gasoline (and trying to use Chevron or Texaco with Techron in it) caused the problem to go away. Putting some tanks of a non-Tier gas back in would cause the problem to reappear.

Would be interested in hearing about similar experiences!