Need help with P0420 - Toyota Nation Forum : Toyota Car and Truck Forums
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post #1 of 19 Old 06-16-2019, 11:53 AM Thread Starter
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Gen5 Need help with P0420

Toyota Camry 2.4L LE.

Other day engine light came on with P0420 code. I have never disconnected the battery terminal but all 4 emission test came on:
  1. evep not ready,
  2. Catalytic converter not ready,
  3. O2 one not ready
  4. O2 two not ready.

My O2 one upstream sensor is steady with 3.3V

But my O2 downstream sensor all over the place jumping from .7V/.8V to downwards.

How do I know that it's my catalytic converter or one of the two Oxygen sensors?

Last edited by inchica2009; 06-16-2019 at 11:56 AM.
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post #2 of 19 Old 06-16-2019, 01:10 PM
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Many things can cause p0420, start with the low hanging fruit or free fix, such as pcv cleaning, engine air filter and gas cap. If you have techstream, you can see the graphs for afs and o2s, when rev engine to 3000 rpm, the graphs would fluctuate, afs and o2s would be reciprocal of each other

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post #3 of 19 Old 06-16-2019, 01:37 PM
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Do some snap throttles while watching A/F and O2 sensor voltages.
If they move normally then sensors good.
A/F should move low 2.5v to high 4.5v from a steady 3.3v with snap throotles.

O2 sensor should move from .2 to .8 from around a study .6v with snap throttles.



What year Camry/miles?
Exhaust leaks around O2 sensor?
Fuel trims normal? Within plus/minus 10 adding ST and LT together.
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post #4 of 19 Old 06-16-2019, 02:47 PM Thread Starter
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Originally Posted by cj1 View Post

What year Camry/miles?
Exhaust leaks around O2 sensor?
Fuel trims normal? Within plus/minus 10 adding ST and LT together.
2003 Camry with 203K mileage. New filter , new PCV valve.May be bad gas cap?

Car drives smooth. No hesitation even though I have this engine light on. I did not even know that emission was incomplete suddenly.

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post #5 of 19 Old 06-16-2019, 03:36 PM
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Maybe bad cat converter if sensors good and no exhaust leak.
If cat original then suspect it has lost its efficiency, thus P0420.
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post #6 of 19 Old 06-16-2019, 04:23 PM
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i believe cj1's correct about the cat. the computer is much more picky on emissions than previous models. run some cataclean through an empty tank a couple of times back to back and see if that turns it off.
tony

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post #7 of 19 Old 06-16-2019, 04:24 PM
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Keep it simple.

Quote:
Originally Posted by inchica2009 View Post
Toyota Camry 2.4L LE.

Other day engine light came on with P0420 code. I have never disconnected the battery terminal but all 4 emission test came on:
  1. evep not ready,
  2. Catalytic converter not ready,
  3. O2 one not ready
  4. O2 two not ready.

My O2 one upstream sensor is steady with 3.3V

But my O2 downstream sensor all over the place jumping from .7V/.8V to downwards.

How do I know that it's my catalytic converter or one of the two Oxygen sensors?
Look very closely for cracks in the ends of your hoses connections on the valve cover. 2003 should have heat cracks right near the connector. Cut 3/8" off and you get to use the same molded hose over (use a better clamp then the existing one)(screw style radiator hose clamp). Pull the map sensor clean it with a dry Q-tip it's probably dirty. (Very Gently) If you haven't changed your air filter this past year do it now also. Pull your plugs to see if any are oil soaked. If so change your valve cover gasket it's a 2 part, and the inner part of the gasket has failed. With the vehicle age and miles it's due anyway. Keep it simple. If you haven't been fudging on your maintenance and oil changes you have another 100'000 before you have to do any real work. Good luck.
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post #8 of 19 Old 06-16-2019, 04:28 PM
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a 420 is a cat code. none of those fixes address a bad/marginal cat. gotta clean it or replace it or lie to the computer (standoff - which I'm not recommending btw) to get rid of that code for very long.
tony

2001 Sienna, 1MZ-FE, A541E
2006 Camry, 2AZ-FE, U250E
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post #9 of 19 Old 06-16-2019, 05:17 PM Thread Starter
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Originally Posted by mcgowaw View Post
i believe cj1's correct about the cat. the computer is much more picky on emissions than previous models. run some cataclean through an empty tank a couple of times back to back and see if that turns it off.
tony

I was thinking about taking it out and cleaning it. Just to see it it makes any difference.

what chemical should I use if I take it out to clean the whole catalytic converter inside out?
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post #10 of 19 Old 06-16-2019, 05:55 PM Thread Starter
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Originally Posted by Fran Grysko View Post
Look very closely for cracks in the ends of your hoses connections on the valve cover. 2003 should have heat cracks right near the connector. Cut 3/8" off and you get to use the same molded hose over (use a better clamp then the existing one)(screw style radiator hose clamp). Pull the map sensor clean it with a dry Q-tip it's probably dirty. (Very Gently) If you haven't changed your air filter this past year do it now also. Pull your plugs to see if any are oil soaked. If so change your valve cover gasket it's a 2 part, and the inner part of the gasket has failed. With the vehicle age and miles it's due anyway. Keep it simple. If you haven't been fudging on your maintenance and oil changes you have another 100'000 before you have to do any real work. Good luck.
New valve cover gasket as well as PCV valve. All filter, spark plugs and map sensor were cleaned or changed.I ordered one new gas cap. Looks like rubber dried up and never been changed. I think may be gas cap loose some how.

Buy I will check the hoses near the valve cover gasket to see if cracked or leaking. I keep my engine very clean and all the hoses are in very good condition. Looks new almost.


I want to make sure before I order a new catalytic converter that it's bad for sure by eliminating other issues first.

Lot of time it is simply air leak or bad gas cap. I had same issue with a chevy because of faulty gas cap. Problem went away after putting a new gas cap.

Last edited by inchica2009; 06-16-2019 at 06:00 PM.
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post #11 of 19 Old 06-16-2019, 06:45 PM
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Quote:
Originally Posted by inchica2009 View Post
New valve cover gasket as well as PCV valve. All filter, spark plugs and map sensor were cleaned or changed.I ordered one new gas cap. Looks like rubber dried up and never been changed. I think may be gas cap loose some how.

Buy I will check the hoses near the valve cover gasket to see if cracked or leaking. I keep my engine very clean and all the hoses are in very good condition. Looks new almost.


I want to make sure before I order a new catalytic converter that it's bad for sure by eliminating other issues first.

Lot of time it is simply air leak or bad gas cap. I had same issue with a chevy because of faulty gas cap. Problem went away after putting a new gas cap.
from my last p0420/p0430 experience

i agreed with mcgowaw, it is a cat code,
as soon as my cel turn on, i acted immediately, clean pvc, and new engine filter, reset cel, but same code pending after a few hundred miles, though cel is not on. the vehicle drives fines.

after verified with techstream, and found my downstream oxygen sensor lazy after warmed up, went and ordered the $50 denso from rockauto and replaced it, and the pending code went away by itself, and IM status ready, has been a few thousand miles now and no cel.

my strategy was, diagnose before replace parts, specially the expensive one, and i know my cat could be bad, p0420 mean cat under efficiency, but not absolute bad cat, and also found my original oxygen sensor lazy, so i figure i spend $50 first, if still cel, then do further diagnose temperature before and after cat, normally a working cat, there is about 200 or 300F difference once the vehicle is in warm up operating temperature.

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post #12 of 19 Old 06-16-2019, 07:25 PM Thread Starter
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Originally Posted by bronzemaxell View Post
from my last p0420/p0430 experience



my strategy was, diagnose before replace parts, specially the expensive one, and i know my cat could be bad, p0420 mean cat under efficiency, but not absolute bad cat, and also found my original oxygen sensor lazy, so i figure i spend $50 first, if still cel, then do further diagnose temperature before and after cat, normally a working cat, there is about 200 or 300F difference once the vehicle is in warm up operating temperature.
so you found out that your catalytic converter was ok because there was a temperature difference of 200/300 between inlet and outlet?

and your O2 sensor was bad because it was lazy after warming up? But O2 should stay steady after warming up. What did you mean by lazy O2 ? did you mean it was almost zero or not responding?

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post #13 of 19 Old 06-16-2019, 08:13 PM
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here was my sequence of diagnostic

as soon as check engine light came on
i cleaned pcv valve, replaced engine air filter and put new silicone grease on gas cap o-ring, then reset cel light

but code remain pending after a few hundred miles

so i begin using tech stream and monitor the afs and o2 sensor, afs range will be 2 to 4v, and o2 sensor 0 to 1v, they all fluctuates, but with a pattern, as i mentioned before, reciprocal,
i've seen as i rev engine to 3000 rpm in parked, the afs will approach 4 while o2 drop to 0, or vise versa, and at idle, afs 3.3v and o2 0.7v.
tech stream has test feature built-in, i was able to do rich and lean fuel test. while i see afs is responding to rich and lean condition, the o2 sensor was not very responsive, (lazy),
as i mentioned before, it can really a bad cat or o2 sensor and many other things, but i figure spend the $50 denso o2 sensor first to eliminate o2 sensor problem, if that doesn't fix it, then i will bite the bullet and get a oem cat at the last resort

after i replaced the o2 sensor, techstream shown my afs temperature 997F and o2 temperature 808 when i raised engine rpm to 3000 for a few minutes.
those sensor temperatures are not absolute, it varies depend engine rpm. i've seen as low as 600 at o2 sensor during idle.
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post #14 of 19 Old 06-16-2019, 08:27 PM
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here is just my opinion, i don't do auto repair for living, and neither good at it

i found many time, as as as the cel turn on, address the problem asap,
when cel is on, vehicle cpu send signal to system to go limp mode, and send more fuel than needed, make it run rich, and those unburnt fuel eventually make its way to the cat, and causing it to melt those honey comb and cause blockage.

when the o2 sensor pattern follow the afs, that mean o2 see exactly what afs see, (cat has lost its function, same temperature goes in, same temperature come out, bad cat)

in my case, my o2 was still responding, but a little delay, therefore, i took the chance and replace o2 first, and it has fixed my problem.

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post #15 of 19 Old 06-17-2019, 12:18 PM Thread Starter
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If you have techstream, you can see the graphs for afs and o2s, when rev engine to 3000 rpm, the graphs would fluctuate, afs and o2s would be reciprocal of each other
I filled up my gas tank, put one bottle fuel system cleaner. Out of four now only one showing incomplete.Cleared my DTC.


1. Evap system incomplete



I think other two will disappear also. I remember last time all 4 incomplete came on when I disconnected my battery.I think disconnecting battery reset memory.

I have to figure it out whether I have any vacuum leak.

Last edited by inchica2009; 06-18-2019 at 01:44 PM.
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