I have an 06' 4runner with 300k miles. I'm getting these two check engine codes, Catalyst Efficiency below normal in bank 1 and 2. I've reset it a couple times by disconnecting the negative battery cable, but it always comes back within 20 miles and now I need to pass inspection. I've been reading threads on this, and can't really come to a conclusion on my best course of action. At first I thought I should try changing the 02 sensors, but it seems faulty 02 sensors have their own error code. Is that where you all would recommend starting? Replacing the sensors? Really hoping I don't need a new cat.
What should my next steps be? P0430 and P0420
- Thread starter kevin1285
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zonianbrat
New member
I went through this recently. I had the 0420 code usually but then the 0430 came in a time or two. The CEL comes on when the cats are reading some ridiculous number of like below 95% efficient. After knowing this I took my temp gun and got the truck to running temp and starting taking temps on the cats. The one on the driver side just under the driver seat had an inlet of close to 500 degrees but outlet was only 230. I am not a mechanic but I believe that one is the culprit as all the other ones were close to 500 going in and coming out. I ran high octane fuel with octane booster and ran it hard down the interstate on the way to the emissions place and cleared the code with my phone before going in. The truck passed and was well within state limits for Colorado. Lights came on like 30 miles down the road again. Just sharing my story and letting you know that just because your CEL is on with the 0430/0420 code it doesn't necessarily mean your truck is below state emissions standards. It's worth a shot to test it and verify it fails before spending lots of cash to throw parts at it that it really doesn't need. Good luck and keep us updated.
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preacher35
New member
Kevin, I JUST went through this the past 48 hours. My '05 was throwing P0430 (bank 2 cat converter). I purchased a new downstream O2 sensor ($90.00 Bosch), installed it (took 4 minutes to do), unplugged the battery to reset the ECM, and drove it for 105 miles. No more CEL/VSC Trac lights. I am cautiously optimistic that this was the problem.
You should purchase at least ONE downstream O2 sensor and try it on both sides and have someone with an ODBII scanner check to see of the codes cancel out. Hopefully, this will resolve your issue!
Preacher
These two codes indicate the cats are dirty, plain and simple. Cats get dirty and eventually get more and more clogged. They need to be cleaned which is something most of us are not willing to do so we end up replacing them. They can be washed and cleaned but the PITA factor is just too high to do this. O2 sensors have their own code when they start to fail, which is usually related to their heaters.
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preacher35
New member
No, not necessarily. As I stated in my earlier post, mine was throwing P0430 and it turned out to be the downstream O2 sensor. If the downstream O2 sensor is faulty, it is not going to be able to report accurate catalytic converter data back to the ECM, or no data at all. This will result in a P0430 or P0420 code. I am not the only one on this forum that has had this same issue and resolved it with a simply O2 sensor replacement. But yes, it COULD be his cats. So why not try the cheaper, easier option first?
This confirms the conundrum I'm facing, seems it can be the 02 sensor or it can be the cats. I'll try the sensor first and go from there. I figure it's probably not a bad thing to do anyways since these are the original sensors with 300k miles. State emissions requirements are a pain in the ass.
That's a good plan, start with the least painful/cost items first.
J-Roc
New member
I live in southern Ontario Canada...Required to do an emissions test every 2 years. I have had these 2 codes for aprox 6 months now and my e-test was due a while ago. Dreading the worst and assuming I was going to have to sink at least a thousand or two into new CATs just to get relicensed for the year. Took it into my shop for the test and bad news. Even drove around for a few weeks with expired tags assuming I was going to have to pay lots when it came time to passing.
Turns out, our laws for these tests are ridiculous...Since it would cost over $500 to make my truck "pass" the test...I was given a "conditional pass" and had to just pay for the failed test itself.
I know this still doesn't solve the issue of the codes and what's wrong, and I do know that one of my CATs is bad. At least I can still drive legal for the next two years before this comes up again.
Check the laws in your area, and it may buy you some more "saving up money" time to fix the real issue. O2's or CATs.
Turns out, our laws for these tests are ridiculous...Since it would cost over $500 to make my truck "pass" the test...I was given a "conditional pass" and had to just pay for the failed test itself.
I know this still doesn't solve the issue of the codes and what's wrong, and I do know that one of my CATs is bad. At least I can still drive legal for the next two years before this comes up again.
Check the laws in your area, and it may buy you some more "saving up money" time to fix the real issue. O2's or CATs.
I might be attempting that on the GF's '08 limited V8 this spring. These cats aren't easy to clean by the way they're attached to the down pipe.
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Anteupp
New member
went through the exact same problem with my tacoma and Honda, save yourself the headache, the few hundred if not thousand dollars and get yourself a set of spark plug non foulers from autozone and do the "non fouler mod" explained here.
https://www.youtube.com/watch?v=wcDPAfz10Io
Don't double up the spacers like this guy did, one will do. Guarantee you pass especially if your state doesn't test the actual exhaust gases coming out of the tailpipe, if those are above your states accepted pollution levels and they test those you're SOL. Good luck
https://www.youtube.com/watch?v=wcDPAfz10Io
Don't double up the spacers like this guy did, one will do. Guarantee you pass especially if your state doesn't test the actual exhaust gases coming out of the tailpipe, if those are above your states accepted pollution levels and they test those you're SOL. Good luck
oljedi11950
New member
Much cheaper to replace all 4 ! Although the a/f sensors are a nightmare , well worth it to change same time ! Or spend money on the URD plug & play rear sensor simulator ! Very rarely cats why peps be stealing off Tacos & 3rd gens Platinum in them !
oljedi11950
New member
^^ this is much CHEAPER !
I ended up buying two of these
https://www.amazon.com/O2-Sensor-Sp...56&sr=1-2&keywords=universal+02+sensor+spacer
Definitely seems to be the way to go. From what I've read this works about 90% of the time. We shall see.
https://www.amazon.com/O2-Sensor-Sp...56&sr=1-2&keywords=universal+02+sensor+spacer
Definitely seems to be the way to go. From what I've read this works about 90% of the time. We shall see.
Hopefully they'll work for the OP but they didn't work for us :-( My GF is still having the P0420 & P0430 codes.
I don't think I'd mess with the upstream A/F sensors as they are not responsible for the P420/P430 codes, rather those sensors are used to control the engine operation.
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oljedi11950
New member
2 down ! Only reason I changed my a/f was told when the downstream start going bad the readings on a/f start going high & also give off codes not sure of that but all mine have been fine since i did it idk ! I know I still was getting cel even after changed lower o2 .
You're correct Kevin, the downstream O2 sensors are the cause of P420/P430 codes.
