OBD II Codes P0420/P0430, 2003 Highlander 2.4L

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My girlfriend has a 2003 Toyota Highlander with the 2.4L (4 cyl) engine that is shared with other models. The thing seems to have a knack for lighting the CEL. This time my cheap-o code reader finds codes P0420 and P0430. This appears to be "Catalyst below efficiency threshold." when I did some online research I saw that it WAS the catalytic converter most frequently, but there were also possibilities of O2 sensors, exhaust leak(s), bad injector(s), spark plugs, etc. The car has around 150,000 miles on it. I erased the codes to see how long it would take for them to reappear - assuming they do reappear. My plan was to get under the thing and check the exhaust system for any leaks or looseness. Also, we might try a bottle of Cataclean. I was just wondering if anyone here had dealt with this issue on this engine or vehicle and what they did to resolve it. Also, has anyone used Cataclean and had good results? If not, can you recommend anything else to clean the converter and squeeze a bit more life out of it? Thank you for your time!
 
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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!)
 
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Calm down dude your going to have a stroke.. 99% huh? and clean a cat? lol it very well could be the post cat sensor sure,have had this problem multiple times over the years,catalytic converters don't die there killed so the chances hers is bad is very unlikely.
 

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The Toyota dealer replaced multiple O2 sensors on this car about three years ago. I believe it has three total. I'll see if she can locate the paperwork to determine if the post sensor was one that was replaced. She did have the code for multiple bad O2 sensors before they replaced them, though. I know how Vikas feels! On my old Honda Accord forum it seemed like every time someone posted something about leaky injectors some genius would tell them to replace the injector o-rings. Those injector would actually leak between the plastic and metal portions of the body and they just had to be replaced. I got to the point where I was responding just like above. LOL. I am almost sure I hear of this stuff on here... http://catacleanus.com/ I usually don't go for stuff like this, but I think there have been decent results.
 
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A plug change/injector clean can often solve the problem, the codes relate to what's coming OUT of the converter, if it's dirty going in, the converter may not clean it enough to pass the "post cat" sensor inspection. A new sensor will probably be MORE sensitive and therefore more trouble. One of our Camrys which sees a lot of low speed driving will show this code, especially in colder weather, a good blast down the interstate and the code will not reset for months, even without a tuneup. I am told the trigger level for the code varies a bit on some Toyota models and the 4 cyl engines are especially likely to set it with a cat which ISN'T about to fail.
 
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The point I'm making is....it could be,Ive had it happen more then once, just recently on my 3500 GMC,catalytic converters rarely go bad. its something upstream causing or sensor. Good luck.
 
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Listen man, this is a possible cheap fix. I had the P0420 code in my Nissan for 2 years. First 3 months, it came off and on, then after that, it stayed on for the next 20 months solid. I never fixed it. I put two bottles of Gumout Regane High Mileage in my 14 gallon tank. About 100 miles later, the code went off. It's stayed off. First time in 2 year!! This was also the first time I had ever put PEA in my gas during that time. The post cat oxygen sensor was dirty and not reading correctly. The PEA made it all the way back there and cleaned it up. Cost me $10. Its not gonna hurt anything. I guess the PEA could have cleaned my cat too.
 
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Shouldn't have a P0430, thats bank 2 of a V6. If your seeing that, I question scanner compatibility. P0420, yeah thats the catalyst efficiency code. Common on that engine, ECU threshold to trip the light is really high. Cats probably still ok. Caused by burning oil for thousands of miles. Usually valve seals, clogged piston oil returns, running low on oil, extending dino oil changes way too far. Best thing to do is the $6 spark plug antifouler trick. I've been running one in my 2AZ-FE I4 2.4L for over 100k now.
 

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She uses the Murphy (Wal Mart) gas. Not that there is anything wrong with that, of course. I also suggested that she run some top tier fuel through the thing. That might help, too. The CEL did not come back on today, but she only has a six mile round trip on Wednesdays. We'll see what happens tomorrow when she will have a twenty mile round trip. I think the first things to try are higher detergent gas and then some PEA cleaner (Techron or Regane). Next, I might try the Cataclean stuff. She just passed her inspection last month so we have some time to play around.
 

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Originally Posted By: LeakySeals
Shouldn't have a P0430, thats bank 2 of a V6. If your seeing that, I question scanner compatibility. P0420, yeah thats the catalyst efficiency code. Common on that engine, ECU threshold to trip the light is really high. Cats probably still ok. Caused by burning oil for thousands of miles. Usually valve seals, clogged piston oil returns, running low on oil, extending dino oil changes way too far. Best thing to do is the $6 spark plug antifouler trick. I've been running one in my 2AZ-FE I4 2.4L for over 100k now.
I am the one doing the oil changes. Seems like it consumes about 1.0-1.5 quarts, total, during an 10,000 mile OCI. And, you are right about the scanner. Mine is a $40 cheapie from Costco. Current fill is 5W-30 PU. I changed the valve cover gasket at the last OC and the valve train, at least, was clean. I use only synthetic oils.
 
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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!)
You beat me to it..and hit it on the NAIL my friend! People are always quick to blame the o2 sensor when it is actually doing it's job by reporting the bad cat converter. I just changed a converter out on a 2004 CTS for the P0430 and the GM manual specifically says NOT to replace any O2 sensors unless they have a related code. Further more, just clearing the code will only work for a while until that OBD test monitor runs again and it can take quite awhile making you think all is well when it is not - the test just hasn't run yet. This Converter on the ops truck will need replacing.
 
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Originally Posted By: daman
Calm down dude your going to have a stroke.. 99% huh? and clean a cat? lol it very well could be the post cat sensor sure,have had this problem multiple times over the years,catalytic converters don't die there killed so the chances hers is bad is very unlikely.
Post sensors rarely go bad..and they will set their own code when far enough out of spec. True, converters are killed...but anyway you look at it - it's dead. We don't know the shape the engine is in on this toyota..it could be burning oil and that will kill a cat pretty fast.
 
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Originally Posted By: DBMaster
She uses the Murphy (Wal Mart) gas. Not that there is anything wrong with that, of course.
That is the WORSE gas I've ever seen.
 
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OK guys here is the science behind it, you can Google it to get it explained better than I could ... All OBD-II cars have mandated O2 sensor after the catalytic converter. Its sole job is to make sure convertor is able to operate at peak efficiency. On many cars that threshold is too high i.e. it insists on >90% efficiency. This is really not necessary as the actual tail pipe emission will be still negligible as required by the FTP. The way computer sets the code is to monitor the rate of switching of the rear O2 sensor. If it starts switching fast or if the switching pattern of the rear O2 sensor starts resembling the front O2 sensor, then computer realizes that converter is not doing its job. Usually this particular test is done when you take your feet of the gas pedal during a steady state cruise on highway. There are bunch of either criteria but this is the important one. So, in theory a bad *front* O2 sensor could indeed fool in to computer thinking that your catalytic converter is bad but in actuality by the time your front O2 sensor has become that lazy, you would have real drive-ability problems. Now if somehow you move the *rear* O2 sensor out from the stream (O2 sensor extension) it starts switching *less*. This makes computer happy. When O2 sensors go to die, they don't become more energetic but rather they become lazy. By putting the sensor extension, you are making that sensor artificially lazy. That is why that method works. You can find many testimonials of that "completely illegal and will get you in federal slammer" scheme. That is why I become so irritated when somebody tells to put new rear O2 sensor to fix P0420/P0430 codes. Science tells you it is wrong and I hope I have explained it why. Get a scanner which can display both the O2 sensor output graphically. Get it on the highway and have somebody else watch the graph during the coasting and it would be apparent if rear O2 starts switching fast. P.S. Good fuel system cleaner could in theory clean up the *front* O2 sensor (it is a stretch) and the converter but it will have a hard time reaching to the rear O2 sensor. There is not enough precious material in the cheap aftermarket convertor to keep the light off for more than 6 months. If you are smart enough, you would have read between the lines and would know exactly what to do to get rid of P0420/P0430 but *I* will not be the one to tell you :-) The 4-cyl engine has single bank, so you should only P0420. Also it can NOT have 3 O2 sensors.
 
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Vikas is spot on about changing the rear o2. Don't. Leave it clogged up and lazy. What the modded spark plug non-fouler (also called anti-fouler) recommendation does. Moves the rear o2 sensor out of exhaust flow and covers the sensor probe. Out goes the light. The front o2 could trigger a P0420 with a cat already on the edge by overwhelming it with raw fuel if the o2 becomes lazy and sets the fuel mix wrong. Its almost never the problem. Usually the cat going below 90-95% efficiency. I'm surprised at your consumption, normally oil is the culprit. Good job! Yes, use a PEA additive like techron concentrate or one of the other PEA's at the end of every oil change. Will help with fuel burn (injectors, combustion chamber, valves, etc) Using one of these additives more often means you don't have to worry about top tier as much.
 
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Yes, Vikas is correct and I agree 100% as a GM engineer. Off topic note: The CTS cat that I recently changed I did use an inexpensive Davidco exact fit converter that was $150 shipped vs 3x that much from the stealer. This was based on the woman's budget and the car being and '04. She is supposed to trade it in the spring for a new car. So far, it's been a few months and all is good. It does have 5 yr/50k mile warranty on the unit itself (steel, welds etc) BUT only 25k miles on "meeting all EPA standards", lol.
 
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