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This video is a little different that the normal ones I do. In this one I have a '02 Rav4 brought in that has already had a lot of fingers in it and the primary problem is the fact that it won't run a drive cycle. I do a live diagnostic test to see what is wrong. I test an AFR Sensor that I suspected was bad during an earlier test drive. Watch the video for the rest of the details! Thanks for watching and subscribing!
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50 thoughts on “Toyota afr / 02 sensor problems”
  1. Avataaar/Circle Created with python_avatars Carlos Rivas says:

    I have a 2006 Toyota Sienna 2006 with the 3.3 engine. For about 9 years I've been having the famous po420. Every 2 years that I renew my tags I have to get my smog check done. What I've been doing is reset the codes with my scanner and go drive it for about 1 hour and go straight to the shop and get my smog check before the codes appears again. Some time the bank 1 s2 on the voltage diagram appears as sensor not reading or I assume not working but after restarting the engine a couple of times it shows the voltage 3.5 n 5.8 up n down. I'm guessing not the cat but maybe o2 sensor malfunctioning. It has 247587 miles on it. Have a blessed day amigos.

  2. Avataaar/Circle Created with python_avatars Alan W says:

    howdy Eric, i know this is an very old video, but have you ever had one of these Toyota front A/F sensors cause a bog down type of issue? And im talking about these older 02-04' ish year models. I had one with a p0031 heater circuit code, circuit was open inside sensor, customer refused to fix it due to 270k on the clock, so it was just gotten rid of and I didnt get to put a sensor in it.

  3. Avataaar/Circle Created with python_avatars Stevieboi 61 says:

    thankyou for sharing your expertise.

  4. Avataaar/Circle Created with python_avatars scott McIntosh says:

    Really learned a lot liked the video give me more please Professor Eric O. !!!! Great video !!!!

  5. Avataaar/Circle Created with python_avatars Rickey Racer says:

    Excellent diagnosis friend. I can see why the readings of the o2 sensor used as the AF sensor, would be all over the place, because of the way in which the two of them work are completely opposite. An A/F sensor, or Wide Band sensor, has more range, more precise readings. Although where they differ more so, is that an A/F sensor, unlike the o2 sensor, puts out a higher voltage reading as it becomes Rich, and lower voltage when reading Lean mixtures. (just the opposite of an O2 sensor.)
    So, I am more than curious if in fact, your diagnosis, and repair corrected the vehicle's ability to "run a drive cycle" Did it? Thank You.

  6. Avataaar/Circle Created with python_avatars corkforbrains says:

    Eric.. is there a scope available that wouldn't cost you an arm and a leg and provide enough functionality to make it a worthwhile investment to the home hobbyist? Thanks!

  7. Avataaar/Circle Created with python_avatars JackTannehillPromoter says:

    You can buy those Denso sensors made in the USA or made in China. The one that's made in the USA cost 2½ times more. Maybe the new made in China one was bad and the one you put in was good?

  8. Avataaar/Circle Created with python_avatars james delb says:

    2006 Toyota Camry. Drive cycle wouldn't complete 3 months. Changed the Air Fuel Regulator in the CAT. bingo, one code cleared on the drive home. You're brilliant, and don't sell yourself short; you're a great teacher..

  9. Avataaar/Circle Created with python_avatars FrugalPrepper's Garage & Garden says:

    Great video Eric, 3 years later I am reviewing it because I have to go diag a Yota AFR tonight!

  10. Avataaar/Circle Created with python_avatars FAUSTO GONZALEZ says:

    Great video Eric, amazing how toyota factory trained technicians replaced computers and other parts and didn't think to monitor the AF sensors. In addition during check mode you can confirm the sequence of sensors checked and that need to pass to complete the drive cycle. Amazes me Toyota techs aren't aware to perform this procedure. Eric what is it you think lacks in training their Techs ? Some dealerships go the extra effort for more tech training and some do not ?? Really, unbelievable. Thanks again great video.

  11. Avataaar/Circle Created with python_avatars KW says:

    P1135 Camry 2002 se v6 3.0

  12. Avataaar/Circle Created with python_avatars Coy Carlson says:

    So – after watching this awesome demonstration of your diagnostic abilities – one has to ask why the engineers would not engineer a completely different connector so there is no mistake made as to installing an O2 sensor in place of a AFR sensor. GREAT DEMONSTRATION 👍👍. We know that at least one reason engineers design for an AFR sensor – instead do an O2 sensor – IT MAKES THEM MORE MONEY – a better mouse trap ?

  13. Avataaar/Circle Created with python_avatars Coy Carlson says:

    Would be nice if the engineers would simply label the connectors AFR – also would be nice if they made the connection to connect / disconnect right off the back of the sensor itself .

  14. Avataaar/Circle Created with python_avatars The2Coolest2 says:

    Bit confused why the duty cycle is 66% from the tool when the wave shows 33%. Duty cycle is how long the signal is high no?

  15. Avataaar/Circle Created with python_avatars Adan Arceo says:

    Much appreciate it sir.
    Thanks for sharing.
    I’m struggling with a car that won’t go on close loop.
    I have the cel illuminated and the code is p0132, circuit high voltage.
    I did Check resistance in the heater circuit and looks ok, I also check the ecu signal coming in the 02 and out and seems to be fine but the car still won’t go close loop.
    Also the 02 sensors bank 1 and bank 2 sensor 1 for each bank read rich condition.
    At this point I’m out of ideas.
    Any advice will be greatly appreciated.
    Thanks in advance.👍

  16. Avataaar/Circle Created with python_avatars Best Clip Ever Misaq says:

    So i got p0420 catalyst system efficiency below threshold bank 1 so which o2 sensor is bad? I have 2014 nissan patfinder v6 awd should i change the o2 sensor by firewall side or the one by radiator side?

  17. Avataaar/Circle Created with python_avatars Hola! drmikeosgood says:

    Hi, how in hades does one know if it is a 02 sensor or an air flow sensor??

  18. Avataaar/Circle Created with python_avatars IMPERATOR-MAXIMUS says:

    GOD JOB 👍KLAUS GERMANY BERLIN

  19. Avataaar/Circle Created with python_avatars asiz direct says:

    Mister sir what do you call a drive cycle

  20. Avataaar/Circle Created with python_avatars Antonio Claudio Michael says:

    Wonder who put the Toyota Avalon oxygen sensor aka o2 sensor in this Rav 4 that requires an Air Fuel Ratio Sensor 🤔 🤔 would be funny if the Toyota dealer put the o2 sensor in LMFAO 🤣🤣 Eric O @SouthMainAutoRepairLLC

  21. Avataaar/Circle Created with python_avatars Antonio Claudio Michael says:

    Definitely looks like the Air Fuel Ratio Sensor Bank 2 sensor 1 is Bad Not responding very well at all Eric O @SouthMainAutoRepairLLC

  22. Avataaar/Circle Created with python_avatars Antonio Claudio Michael says:

    Is this the same Rav 4 That you did the head bolt repair and Head Gasket On Eric O @SouthMainAutoRepairLLC

  23. Avataaar/Circle Created with python_avatars Antonio Claudio Michael says:

    Pore customer, It won't run a drive cycle and the parts cannon has been shot at it from every shop including the dealer Now Eric O to The Diagnostic Rescue @SouthMainAutoRepairLLC

  24. Avataaar/Circle Created with python_avatars Blake Ogle says:

    Thank you for making this video

  25. Avataaar/Circle Created with python_avatars FAUSTO GONZALEZ says:

    Eric, my understating is that when you're reading an AFR signal in OBD II mode, you get 1/5 the value of the AFR reading in Enhanced MODE. Therefore, if the Enhance mode reading of the AFR sensor is 3.3 Volts, in OBD II mode you will read the AFR Voltage as 0.666 V which equals 3.3v/5v = 0.66 Volts, in addition during acceleration in OBD II mode, the AFR signal in OBD II value will display about 0.5 V, which equals a AFR Voltage (enhanced mode) of 2.5 V (equals rich mixture); therefore 2.5 V/5V = 0.5 Volts. Also, as you mentioned, further testing and confirming the AFR sensor is operating correctly, you could remove the harness side connector of the AFR sensor, put the probes of a VOM or a Scope between the two signal wires of the AFR sensor (while AFR sensor is still in exhaust pipe) , jump the two heater wires from the disconnected Harness connector to the heater wires on the AFR sensor heater wires ( helps keep the AFR sensor at optimum Temp while conducting this test) , you will get an Analog signal ranging from about 0.8 V to about 0.2 V just like a Narrow Band O2 sensor. This confirms the correct operation of the AFR sensor if you do not have the ability to Read Enhanced mode data. Thanks for the great video!!! What Amazes me is how is it an ASE Certified Toyota Dealership Tech could not identify and confirm a faulty operation of this AFR sensor, Amazing !!!!!!!!!!

  26. Avataaar/Circle Created with python_avatars 2 Ol' Vets says:

    What would sensor 2 look like on the sin wave and voltage? Would it graph like sensor 1 or would it jump around more?

  27. Avataaar/Circle Created with python_avatars Reza ZMJ says:

    thats great thanks alot

  28. Avataaar/Circle Created with python_avatars corvettebob says:

    Just found this gem after watching 100s of newer videos. I understood everything you were explaining and enjoy your in depth analysis. I have no clue if I will ever use it in my lifetime….

  29. Avataaar/Circle Created with python_avatars RAMON GONZALES says:

    Thats sad a toyota dealership couldn't figure that out

  30. Avataaar/Circle Created with python_avatars Screw Ball says:

    So I guess I assume on my 2.4l 05 toyota camry the afr is probably bad since it jumps up to 5 v at about 2k rpm. At idle it's about 3v and it idles about 680 rpm

    It takes forever to run a drive cycle but when it does pass sets off a p420 code.

  31. Avataaar/Circle Created with python_avatars Ray Man says:

    Good info as usual

  32. Avataaar/Circle Created with python_avatars Hal Burdick says:

    I would call this a surprise ending. Wrong part!

  33. Avataaar/Circle Created with python_avatars paul pagano says:

    I have a 2007 Camry with a 420 code and owner says it's using excessive fuel . I have an Autel 808 scanner. should I start with looking at AFR sensors ? thanks !

  34. Avataaar/Circle Created with python_avatars RFDarter says:

    Whats meant by a drive circle?

  35. Avataaar/Circle Created with python_avatars Peter Najduk says:

    well done coach

  36. Avataaar/Circle Created with python_avatars John Schuler says:

    Well Done! Love it. As a EE, I am most impressed with your knowledge and actions. Plus you do a fine job of SHOWING and EXPLAINING things! On my own 2003 Lexus RX300, I had a code for B2 S1 AFR. $125 for a Denso. Change other one, Plus O2 $50 for Denso for preventive maint.

  37. Avataaar/Circle Created with python_avatars Bryan Toth says:

    You don’t need no stinkin’ ASA certificate.

  38. Avataaar/Circle Created with python_avatars Gera Grabovich says:

    Ha I was just letting YouTube play videos for me and this came across. I fixed an 02 Avalon for this same problem yesterday. Only complaint was an abnormal shift.

  39. Avataaar/Circle Created with python_avatars Silas Kok says:

    Great video Eric! Very informative. Question, I have a 2000 4runner that's giving me a P0420 code (california emissions) I've already replaced forward a/f sensor with no luck. Do you think I should try replacing the rear 02 sensor, or should I be more focused on the wiring harness to the a/f sensor?

    any advice would help, thank you

  40. Avataaar/Circle Created with python_avatars Kim Robinson says:

    Hi Looking at a RAV4 2002 it has Sensor 02, on Engine light is on and brake light the dealer said maybe needs struts?
    I am wanting to upgrade to a 4w/d from fwd my RAV4 has 116,000
    My a/c is gone they had seal, etc.
    What do you think about all of this? Thank u!

  41. Avataaar/Circle Created with python_avatars WmTyndale says:

    Very Very Useful!

  42. Avataaar/Circle Created with python_avatars tom mendoza says:

    Thank you, excellent teaching. 👍

  43. Avataaar/Circle Created with python_avatars Aaron Sanchez says:

    Love the video thanks for the advice….i just ordered the correct air fuel ratio o2 sensors they are pricey but im getting the right ones hopefully my 01 rav will act right now

  44. Avataaar/Circle Created with python_avatars tim says:

    I have a 2000 4runner 3.4 4wd A/T limited California emissions.. with a p0135 (sensor 1 heater circuit) but all the info for that code says a p0135 is except California emissions??

  45. Avataaar/Circle Created with python_avatars Willis Johnson says:

    You was greener than some well watered South Florida grass… 🤣

  46. Avataaar/Circle Created with python_avatars MM Reporter says:

    Really enjoy the analytics Eric. Makes the gray matter work a little harder to stay with you. Good job on this video…..

  47. Avataaar/Circle Created with python_avatars Epitacio Basurto says:

    You did great in this viveo. Thanks Because I have tha verus

  48. Avataaar/Circle Created with python_avatars TIMINGBELTS says:

    You are a great teacher . i learn more from you than others. Thanks!!!!

  49. Avataaar/Circle Created with python_avatars Timetryp says:

    Other mechanics just throwing parts at it – guess work. Too bad the owner didn't see you first and get it done right then.

  50. Avataaar/Circle Created with python_avatars Maxim Teleguz says:

    How do you put a Toyota in check mode?

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