P0420 catalyst efficiency low
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Joined: Aug 2009
Posts: 34
Likes: 8
From: illinois
P0420 catalyst efficiency low
First off, thanks, this forum is a great resource. Forgive me if this is too long:
We've had our 2001 since new and it has 123,000 miles. I fix everything promptly, and we've experienced a lot of the common problems.
Perhaps relevant here: an upgraded rear valve cover at about 100,000 miles eliminated the common oil guzzling problem, and we didn't ignore the problem and allow it to persist. I did the timing belt/WP and spark plugs at the same time. I replaced both A/F sensors and some leaky exhaust gaskets a few years ago, and all was well.
A few weeks ago, we noticed an occasional, slight, single hesitation (like a bump) when pulling away from a stop with the engine warm. No CEL, so I thought the trans wasn't engaging right, but I was confused because it was intermittent. Finally we got a code for the front bank VVT solenoid, which I replaced along with the rear one. I did drive it home in limp mode for less than a mile with a flashing CEL...
After the VVT solenoid replacement, that code did not return, but the "bump" still happens, albeit milder and rarer. Then today, code P0420 came up, catalyst efficiency low. I saw recommendations to change the [still original] downstream O2 sensor, so the old one is off and new one is on the way. If the P0420 returns, the recommendation seems to be to replace "the" catalytic converter, but that leaves me confused:
1) Of the three converters, are folks replacing only the one downstream? Since there's only one downstream sensor, how does anyone know which of the three catalytic converters may be bad?
2) There are no other codes. Can I be confident that everything's OK upstream, like mixture, ignition, etc...? I ask because the slight hesitation is a driveability issue, and the catalytic converter and O2 sensor shouldn't affect that unless the cat(s) are plugged, in which case I'd expect poor mileage, loss of power, other codes, etc... We have none of that.
3) Did that remote oil consumption problem ruin the catalytic converter(s), only to crop up so many years later?
4) Did driving 1 mile with a failed front bank VVT solenoid ruin one or two of the catalytic converter(s)?
P.S.: I think it's odd I got the P0420 code so soon after the VVT solenoid replacement, but the job went smoothly. Any opinions on that? Coincidence seems unlikely...
We've had our 2001 since new and it has 123,000 miles. I fix everything promptly, and we've experienced a lot of the common problems.
Perhaps relevant here: an upgraded rear valve cover at about 100,000 miles eliminated the common oil guzzling problem, and we didn't ignore the problem and allow it to persist. I did the timing belt/WP and spark plugs at the same time. I replaced both A/F sensors and some leaky exhaust gaskets a few years ago, and all was well.
A few weeks ago, we noticed an occasional, slight, single hesitation (like a bump) when pulling away from a stop with the engine warm. No CEL, so I thought the trans wasn't engaging right, but I was confused because it was intermittent. Finally we got a code for the front bank VVT solenoid, which I replaced along with the rear one. I did drive it home in limp mode for less than a mile with a flashing CEL...
After the VVT solenoid replacement, that code did not return, but the "bump" still happens, albeit milder and rarer. Then today, code P0420 came up, catalyst efficiency low. I saw recommendations to change the [still original] downstream O2 sensor, so the old one is off and new one is on the way. If the P0420 returns, the recommendation seems to be to replace "the" catalytic converter, but that leaves me confused:
1) Of the three converters, are folks replacing only the one downstream? Since there's only one downstream sensor, how does anyone know which of the three catalytic converters may be bad?
2) There are no other codes. Can I be confident that everything's OK upstream, like mixture, ignition, etc...? I ask because the slight hesitation is a driveability issue, and the catalytic converter and O2 sensor shouldn't affect that unless the cat(s) are plugged, in which case I'd expect poor mileage, loss of power, other codes, etc... We have none of that.
3) Did that remote oil consumption problem ruin the catalytic converter(s), only to crop up so many years later?
4) Did driving 1 mile with a failed front bank VVT solenoid ruin one or two of the catalytic converter(s)?
P.S.: I think it's odd I got the P0420 code so soon after the VVT solenoid replacement, but the job went smoothly. Any opinions on that? Coincidence seems unlikely...
Thread Starter
Rookie
Joined: Aug 2009
Posts: 34
Likes: 8
From: illinois
I don't know if this'll help anyone, but while waiting for the new sensor, I looked for upstream exhaust leaks, with the hopes that the catalytic converters are not the cause of the code, since the car really has had a pampered life.
At first I didn't hear anything, and the gaskets I replaced years ago are fine. However, when I tugged at the flex section under the engine... Wow! Massive leak! The flex section is broken open in multiple places. The car sounds fine when we drive it because the pipes still line up nicely. I have a good flex joint from another car project that will fit well, while I'm welding that, I'll also weld a small crack at the exhaust hanger between the rear catalytic converter and the resonator.
Hopefully that and the new sensor will solve the P0420 code. If not, I'll think about changing all three catalytic converters. Rockauto has everything and it adds up to $732, which I think is worth it on this car. Maybe the old ones aren't too bad to remove...
At first I didn't hear anything, and the gaskets I replaced years ago are fine. However, when I tugged at the flex section under the engine... Wow! Massive leak! The flex section is broken open in multiple places. The car sounds fine when we drive it because the pipes still line up nicely. I have a good flex joint from another car project that will fit well, while I'm welding that, I'll also weld a small crack at the exhaust hanger between the rear catalytic converter and the resonator.
Hopefully that and the new sensor will solve the P0420 code. If not, I'll think about changing all three catalytic converters. Rockauto has everything and it adds up to $732, which I think is worth it on this car. Maybe the old ones aren't too bad to remove...
Pole Position
Joined: Sep 2012
Posts: 338
Likes: 16
From: Oregon
Do you have one of those laser no-touch thermometer guns? If so you can check each catalytic converter individually by measuring the temperature of the exhaust gases at the input and output of each catalytic converter. If the converter is working the exhaust should be hotter at the output than at the input. I think about 100 degrees or so, but I'm not positive about the exact number.
Thread Starter
Rookie
Joined: Aug 2009
Posts: 34
Likes: 8
From: illinois
I don't have a thermometer, might be time to buy one. Rejuvenation, is that like Italian Tune Up? I've seen that it's possible to burn off catalytic converter deposits with hard driving.
Anyhoo, I'm calling this code solved: replacing the 17 year old O2 sensor and welding in a new flex section (last night, outside in 20 degree weather), and several long drives with time to fully cool in between shows no codes or pending codes, and the driveabiliy issues are gone, for now at least. Not sure why an exhaust hole that I couldn't hear would be a big deal, if the back pressure were that low, I should've heard rumbling.
I think it was the broken flex pipe, not the sensor, since there were no sensor related codes. I never would have found the leak if it weren't for a YouTube video of a guy causing a loud leak there on an otherwise quiet Rx300 by prying at the corrogations with a screw driver.
Thanks for the response, great forum for a great car!
Anyhoo, I'm calling this code solved: replacing the 17 year old O2 sensor and welding in a new flex section (last night, outside in 20 degree weather), and several long drives with time to fully cool in between shows no codes or pending codes, and the driveabiliy issues are gone, for now at least. Not sure why an exhaust hole that I couldn't hear would be a big deal, if the back pressure were that low, I should've heard rumbling.
I think it was the broken flex pipe, not the sensor, since there were no sensor related codes. I never would have found the leak if it weren't for a YouTube video of a guy causing a loud leak there on an otherwise quiet Rx300 by prying at the corrogations with a screw driver.
Thanks for the response, great forum for a great car!
Racer
Joined: Oct 2009
Posts: 1,296
Likes: 320
From: nj
I once had a P0420 when the donut gasket in front of the rear cat was leaking. It was barely audible when I was in an enclosed area.
Replacing the gasket resolved the issue.
More recently I replaced the rear cat with a Wagner one. Pretty sure I contaminated it by ignoring a system too lean for months.
Replacing the gasket resolved the issue.
More recently I replaced the rear cat with a Wagner one. Pretty sure I contaminated it by ignoring a system too lean for months.
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Driver School Candidate
Joined: Feb 2018
Posts: 6
Likes: 1
From: California
According to this guide: http://topautotools.com/error-code-p0420-obd-ii/ you have a few things to check. Start with putting cat cleaner in your gas tank and see if that does the trick because that’s obviously the simplest of the methods.
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