OBD II Codes P0420/P0430, 2003 Highlander 2.4L

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Just remember the programmed catalyst efficiency threshold varies by auto manufacturer. Very high on late model Toyotas. Many Toyota owners complain that aftermarket cats don't last very long. Cheap aftermarket cats are cheap because they usually don't have as much of the expensive catalyst media, so they can't maintain high efficiency as long as the OE cat. So before you replace it, try taking the manifold cat off and cleaning it before using an aftermarket. Assuming the catalyst is not fractured from heat, an overnight dunk in laundry detergent and a rinse works in cases where its not totally clogged from oil consumption, on the edge with a intermittent highway CEL, etc.
 
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Originally Posted By: Vikas
NO, it is NOT the post cat O2 sensor. Aaaaaaaaaaarrrrrrrrrrrrrrggggggggggggggg The way system functions is that if you put a brand new and better O2 sensor, you will get the P0420 quicker! When you get P0420, 99% it is because computer has determined that your catalytic converter efficiency is low. Your choices (not all of them are available to you) 1) Factory reprogram to reduce the trip point 2) Clean the catalytic converter (some home made remedies are floating on the internet; use and tell *us* if they work!) 3) Replace with OEM converter. DO NOT BOTHER WITH A CHEAP AFTERMARKET; the code will come back in less than six months 4) Google O2 sensor extension (If anybody asks, you did NOT get it from me!)
Vikas with all due respect you come up with this all the time and it simply isn't always the case. It is true a older O2 sensor can help resist a 420/430 code but the cat does not have to be defective exclusively to trigger these codes. I did a cat for a guy last year on a Corolla, he insisted it was the cat and wanted no diagnostics done as it was a waste of money. He got this info from the internet. Fine. I a had him sign off on this deal "replace cat for PO420 at customer request, no diagnostics". I replaced it as requested with a brand new OEM unit. Well he was quite PO'd when the light came back on a few miles later and tried to pass it off on me. "I should have told him it could be something else as i am the mechanic and should know better". I told him to back back to his internet pals and get a diagnosis and come back and tell me what he want to replace next before tossing him out. lol. BTW yes it can be a deteriorating (not totally shot) rear O2. Read this.. http://www.easterncatalytic.com/education/tech-tips/pesky-p0420-codes/ http://www.easterncatalytic.com/education/tech-tips/the-misleading-nature-of-the-po42o-code/ http://www.p0420.com/ http://www.aa1car.com/library/p0420_dtc.htm
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Sometimes a faulty O2 sensor is not bad enough to set an O2 sensor code but is off just enough to affect the accuracy of the catalyst monitor.
Yes it is more than likely a bad cat but never swap a cat out without fully diagnosing and testing the cat! Just throwing a cat at a PO420/430 it a mugs game.
 
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I am going to get an OBD scan tool that interfaces with my laptop - this is a good excuse. I am going to check for the two things in the video first, have her run top tier gas, and put through a bottle of PEA cleaner. THEN, we'll look elsewhere. The car is not using enough oil for that to be an issue. I pulled one of two of the plugs when I changed the VC gasket because she had those changed before I started maintaining the car. They are platinum plugs (NGK or Denso, can't recall which) and they look perfect - no fouling at all.
 
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DB use an infrared thermometer on the cat, take the temps at the pipe just before and after it at idle and 2500 RPM. Post the difference.
 
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Trav - Would a fair interpretation of your response to Vikas be.. "never say never, 9 out of 10 times its cat efficiency, but not always"..?
 
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The most probable cause for P0420 and P0430 is the O2 sensors unless one has been running life long on some cheap gas, it would point to a bigger problem. Most cats and pre-cats are designed for the life of the car (say 200K) and O2s can get pretty dirty if run on poor gas. The [censored] codes are mapped onto different mechanical (cats) and electronic (O2s) failures -- it would be easier to root cause it if there were different codes. I would start with the O2s and go from there and start using Shell, Exxon or Chevron gas.
 
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Originally Posted By: LeakySeals
Trav - Would a fair interpretation of your response to Vikas be.. "never say never, 9 out of 10 times its cat efficiency, but not always"..?
I would say something like that, an exact percent i don't know. I do know in the State of MA we had quite a few replaced good cats by garages. We investigated a lot of them because inevitably the customer would come to us looking for an emissions waiver. Many many times we got the answer "it had a PO420/430 so we did what we are supposed to do and put a cat in". Wrong answer.
 

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Originally Posted By: Trav
DB use an infrared thermometer on the cat, take the temps at the pipe just before and after it at idle and 2500 RPM. Post the difference.
I just happen to have one. I bought it primarily to do A/C work - $50 at Sears a few years back. I won't have access to the car until this weekend so I'll let y'all know. She did the ten mile drive to work this morning, the six mile round trip yesterday, and some extra driving around town and the CEL hasn't come back on yet.
 

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BTW, my 89 Accord required actual tail pipe emissions tests every year. It last passed in March of 2012, original cat. I used only good gas in it and would dump a can of Berryman's in the tank once a year. They really overbuilt that generation of Accord!
 

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Originally Posted By: The Critic
You should always check for any applicable TSBs before jumping to conclusions. There's an updated ECM calibration available to address the P0420 code on this car: http://www.toyotapart.com/ECM_CALIBRATION_UPDATE_M.I.L._ON_DTC_PO420_AND_OR_PO430_T-EG041-05.pdf However, at 150k, there's a good chance that it needs a CAT anyway, but the updated calibration is worth a shot and should still be loaded, IMO.
OK, I'll be a pain - just a bit. Two of you said I could not get a P0430 on this engine because it's a 4 and not a V6. That seemed logical to me, however, this TSB states that you CAN get both codes on the 4. She'll probably never find it, but I'll ask her to locate the shop receipt from the Toyota dealer show which sensor(s) they replaced a few years ago. Some dealers cover replacement parts like that for life - IF it ends up needing another sensor. I really appreciate you guys taking the time on this one. I have gained a pretty good education of how the catalyst system works on this car now.
 
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I will play the game with you Trav. You tell me how you proceeded to diagnosis the bad O2 sensor. It was diagnosed and not just swapped, correct? I presume you put a scope on both the front and rear O2 sensor. What waveform did you see which told you the rear O2 sensor was bad? Was it switching too fast? I have no problem when you correct me as you have lot more knowledge and experience in the field. However, I do expect that you would be able to explain and show evidence based diagnostics. For example, you could have observed the rear waveform and it was stuck forever regardless of the engine operating condition and it would then imply bad O2 sensor. The smart engineer who designed the engine management system should then spit out the applicable code rather than throwing the catch all cat converter efficiency code. But we all know how we engineers sometimes just punt. Heck, when I am coding something late at night, I will just return "-1" error and get on my life rather than giving the more specific error code. But in this case, there is indeed P0137 and P0138 code when rear O2 is stuck and you would expect ECM to give that error rather than P0420.
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[P0137] The rear heated oxygen sensor has a much longer switching time between rich and lean than the front heated oxygen sensor. The oxygen storage capacity before the three way catalyst causes the longer switching time. To judge the malfunctions of rear heated oxygen sensor, ECM monitors whether the minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut. Malfunction is detected when the minimum voltage from the sensor is not reached to the specified voltage
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[P0138] The rear heated oxygen sensor has a much longer switching time between rich and lean than the front heated oxygen sensor. The oxygen storage capacity before the three way catalyst causes the longer switching time. To judge the malfunctions of rear heated oxygen sensor, ECM monitors whether the maximum voltage of the sensor is sufficiently high during the various driving condition such as fuel-cut. Malfunction is detected when the maximum voltage from the sensor is not reached to the specified voltage.
Could deteriorated rear O2 sensor start fast switching on its own? Not very likely. May be if the inside wire is on the verge of braking and having flaky connection but that still would not mimic high switching rate. I can not come up with a situation where one could observer bad O2 sensor behavior and the ECM decides to throw P0420 code. Can you? I hope this reply is taken in the intended spirit. Take it like being challenged by an inquisitive student to highly respected distinguished professor than as a urinary throw length contest :-)
 
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Have to share because I just went through this. I replaced BOTH the O2 sensors to the tune of $300 from Amazon, and since then, no light. There are two sensors on the 2.4l...one upstream, one down. I've ran Techron/Redline SI-1 and the code has not come back yet. My 2004 2.4L has 139K miles on it. Passed recent smog last summer, though not by much - if we keep it we will probably have to replace the cat in two years - or get a reflash from the dealer if available. To the OP: I personally believe 10K oci is way too far for this engine. Max for me is between 4-5K, particularly because most of the miles are city miles.
 
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What happens when an rear zirconium dioxide O2 sensor looses or has a reduction with its atmospheric reference signal? It get scatterbrained correct? It is however technically still functioning. Just a thought.
 
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I am not sure how that would cause the rear sensor to incorrectly start switching quicker. Would blocking off the air vents of the sensor lead to this behavior? I honestly do not know if O2 sensor would start switching faster if the air vents on the sensors are blocked or enlarged. I have not seen any authoritative document claiming that. Notice how OEM trouble shooting chart does not even list rear sensor as a possible cause of the catalytic converter efficiency low code
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On Board Diagnosis Logic (for P0420/P0430) The ECM monitors the switching frequency ratio of front and rear heated oxygen sensors. A warm-up three way catalyst with high oxygen storage capacity will indicate a low switching frequency of rear heated oxygen sensor. As oxygen storage capacity decreases, the rear heated oxygen sensor switching frequency will increase. When the frequency ratio of front and rear heated oxygen sensors approaches a specified limit value, the warm-up three way catalyst malfunction is diagnosed. Malfunction is detected when warm-up three way catalyst does not operate properly, warm-up three way catalyst does not have enough oxygen storage capacity Possible Cause I Warm-up three way catalyst I Exhaust tube I Intake air leaks I Injectors I Injector leaks I Spark plug I Improper ignition timing
Once again my ranting was over the suggestion to replace the rear O2 sensor for this code. This was also suggested with no other diagnosis i.e. throw a part. As far as throwing a part is concerned, I had claimed (and still do) that this is incorrect part to throw at this code. You are more likely to have better success rate to throw front O2 sensor to fix this problem than throwing rear O2 sensor based upon the theory of how ECM decides to turn on P0420 code (and P0420 code ONLY!) I am in 100% agreement with you that throwing a new catalytic converter just because there is P0420 code is not the right thing to do unless further diagnosis has been done. Having said that, you need to tell which diagnostic procedure you would have used to condemn rear O2 sensor as bad when the car came to you with P0420 (and P0420 code only). If you are going to say let us just replace the rear O2 sensor and see if the code goes away, then I am sorry to say that is not what I would expect from you.
 
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Back to OP; I thought Highlander also came with V6 engines. I wonder if the TSB writer just cut-and-pasted the section from the other engine. That would explain references to P0430 or the ECM programming really had a bug and referred to non-existent bank 2!
 
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Originally Posted By: MysticGold04
Have to share because I just went through this. I replaced BOTH the O2 sensors to the tune of $300 from Amazon, and since then, no light. There are two sensors on the 2.4l...one upstream, one down. I've ran Techron/Redline SI-1 and the code has not come back yet. My 2004 2.4L has 139K miles on it. Passed recent smog last summer, though not by much - if we keep it we will probably have to replace the cat in two years - or get a reflash from the dealer if available. To the OP: I personally believe 10K oci is way too far for this engine. Max for me is between 4-5K, particularly because most of the miles are city miles.
Can you post the emission results? I am really surprised that the results were so close to limit. They should not be unless the catalytic converter is truly dieing. And if that is the case, reflash is not going to help. Were the NOx too close to limit? Was the car hot and ready? When you were waiting for your slot, was the car turned off? If you have access to a decent scanner which can give the mode 6 data, you can get an idea as to how close you are to failing any of the built-in test ran by the ECM. It is always a challenge to find the decoding ring for Mode6 data but some manufacturer put this on the internet and/or somebody who has access to proprietary information might help you out. Looking at the possible O2 sensor signal error codes, there is not one for "too much activity"! This implies "too much activity" is NOT one of the failure mode for an O2 sensor. This means if the rear O2 sensor is switching too fast, it is NOT because it is broken. Anybody recommending to replace rear O2 sensor when ECM detects too much activity is not dispensing the logical advice.
Code:
P0130....O2 Sensor Circuit Bank 1 Sensor 1
P0131....O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
P0132....O2 Sensor Circuit High Voltage Bank 1 Sensor 1
P0133....O2 Sensor Circuit Slow Response Bank 1 Sensor 1
P0134....O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1
P0135....O2 Sensor Heater Circuit Bank 1 Sensor 1
P0136....O2 Sensor Circuit Malfunction Bank 1 Sensor 2
P0137....O2 Sensor Circuit Low Voltage Bank 1 Sensor 2
P0138....O2 Sensor Circuit High Voltage Bank 1 Sensor 2
P0139....O2 Sensor Circuit Slow Response Bank 1 Sensor 2
P0140....O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2
P0141....O2 Sensor Heater Circuit Bank 1 Sensor 2
P0142....O2 Sensor Circuit Malfunction Bank 1 Sensor 3
P0143....O2 Sensor Circuit Low Voltage Bank 1 Sensor 3
P0144....O2 Sensor Circuit High Voltage Bank 1 Sensor 3
P0145....O2 Sensor Circuit Slow Response Bank 1 Sensor 3
P0146....O2 Sensor Circuit No Activity Detected Bank 1 Sensor 3
P0147....O2 Sensor Heater Circuit Bank 1 Sensor 3
 
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First i never just throw parts at anything especially something as expensive as a cat. First and foremost you need to know if there is a catalytic action taking place. Temp test. Second you want to know if the substrate is melted. Vacuum test and or back pressure test. If any of these things fail the cat is most likely the problem but if they pass its time to look at other possibilities. Using the scope or scan tool look at the rear O2/cat monitor and the front O2/AF monitor . Anything erratic on the rear O2 pattern can cause a PO420/430. The front one will probably not cause this code, the rear O2 is monitoring the cat. Erratic operation can be caused by a ground fault contact due to rust on the threads on non dedicated ground units or an erroneous atmospheric reference signal in some types of sensors. With so many different types of cells one set of parameters cannot be applied to all, eg potentiometric sensors AKA Lambda probes are common in automotive use but do not do well in lean burn conditions so anther type is used in those applications. These require an atmospheric reference. The limiting current amperometric sensor does not require an atmospheric reference and is more common in A/F monitors or front O2. This is all from memory so google it yourself. The OEM Diagnostic chart refers to one particular make or model, there are many different types of rear O2 and front O2/A/F monitors. There are a few other types that i forget, google is your friend as i am not an electronic engineer just a lowly mechanic with dirty hands. Some breath through the cables others from around the shell, some use a dedicated ground other use the pipe (this type will usually use a ground strap on the exhaust). Don't mistake possible cause in a manual as meaning every possible cause. When you have been in this game as long as i have you would know that.
 
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Originally Posted By: MysticGold04
Have to share because I just went through this. I replaced BOTH the O2 sensors to the tune of $300 from Amazon, and since then, no light. There are two sensors on the 2.4l...one upstream, one down. I've ran Techron/Redline SI-1 and the code has not come back yet. My 2004 2.4L has 139K miles on it. Passed recent smog last summer, though not by much - if we keep it we will probably have to replace the cat in two years - or get a reflash from the dealer if available. To the OP: I personally believe 10K oci is way too far for this engine. Max for me is between 4-5K, particularly because most of the miles are city miles.
I spent $6 to cap off my rear o2 off 100k ago. For that reason I suspect your front AF/o2 sensor had you running rich overwhelming the cat with unburnt fuel. depending on when you replaced the sensor, that could have contributed to your poor smog test last summer.
 
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