P0420 and P0430 - Need Help Diagnosing

[S20Workstation4]

Hello All,

My 2010 Ford Expedition EL gave me a P0420 code (Cat Bank 1), about a month ago.

I did a WOT test, no problems there.
I did the mallet test, no signs of broken substrate in the converters (I tested both).
Not too long after, it gave me another confirmed code P0430 (Cat Bank 2). It now has 2 confirmed codes for both cats.

I did a temperature test, and both cats at running at 700 degrees Fahrenheit. This was checked after 30 Minutes of driving and then held at 2,000 RPM while checking the temperature.

I think I have done all the tests possible. Could it still be the cats, or could it be oxygen sensors? It seems odd that P0420 and P0430 would come up almost at the same time. I am at a loss here.

Note: Vehicle was sitting since July because of timing chain rattle, and was just put on the road about 1 month ago. Could the sitting/not driving have anything to do with these codes? Gasoline was stabilized correctly, so no contaminated fuel system.


Any help is appreciated.

-Joseph

 

[Thom]

I have the PO430 code on my 2014 (driver side bank 2). The vehicle runs fine. I have a scan tool with graphing capabilities and with the help of the linked video, I was able to determine the cat on bank 2 just isn't doing its job. My downstream O2 sensor was mimicking the front O2 sensor. which it should not do (see video). But since the vehicle runs fine I might not do anything about it for a while. The temps on the cats were also around 700 and there is no loose substrate. A couple of years ago I had some misfiring going on and this might have contributed to the bank 2 cat demise, not sure.
https://youtu.be/xLyytQD7njw

 

[S20Workstation4]

Thank you for reply, I will check out the video you linked.
I have a BlueDriver OBDII scanner, but it says that I can only transmit live data from the upstream sensors, and it says "not supported by this vehicle", when I go to try and read live data from the downstream sensors.
I may have to bring it to a shop and have them read the voltage for me.

I had a misfire back in November 2019, but it didn't last for long and was very intermittent. I am not considering this misfire as a cause for these codes.

I am going to try and reset the fuel trims and see if it fixes this problem, the vehicle was sitting for quite some time, and then driven below 10mph for only a couple of months, and a lot of idle hours...

 

[TobyU]

Hello All,

My 2010 Ford Expedition EL gave me a P0420 code (Cat Bank 1), about a month ago.

I did a WOT test, no problems there.
I did the mallet test, no signs of broken substrate in the converters (I tested both).
Not too long after, it gave me another confirmed code P0430 (Cat Bank 2). It now has 2 confirmed codes for both cats.

I did a temperature test, and both cats at running at 700 degrees Fahrenheit. This was checked after 30 Minutes of driving and then held at 2,000 RPM while checking the temperature.

I think I have done all the tests possible. Could it still be the cats, or could it be oxygen sensors? It seems odd that P0420 and P0430 would come up almost at the same time. I am at a loss here.

Note: Vehicle was sitting since July because of timing chain rattle, and was just put on the road about 1 month ago. Could the sitting/not driving have anything to do with these codes? Gasoline was stabilized correctly, so no contaminated fuel system.


Any help is appreciated.

-Joseph

I have seen over and over throughout the years people replacing oxygen sensors for these codes when it's actually the converter is just weak.
It's usually not on both sides though.
Normally this is from an ignition cylinder misfire at one time or another that was driven longer than they should have and that damage the catalyst in the converter.
It's possible to have an O2 sensor that's a little out of whack but probably not going to be the case.
You should be able to watch the O2 sensors switch back and forth on a scan tool but all you can really do is compare the rate they switch and maybe see the numbers they pop to unless you have some more sophisticated stuff than most people have and even that's not going to be definitive.
Most of the time it's simply a lazy converter.
I've had good luck with cleaning them a little bit!
They sell that emissions cleaner guaranteed to pass stuff that would probably work but I've actually always been too cheap to use that but I've heard other people say they've had similar results to what I do with it.
I just go get a bunch of the 90 or 92% isopropyl alcohol and I've even used the red Heet.
Note, both of these are harder to find and more expensive now especially the alcohol is hard to find as the only one to give you the 70% or whatever it is.
But I would get two and sometimes three of the largest bottles of the alcohol at the grocery store and dump them in with very little fuel in the tank like no more than 3 to 5 gallons.
Then I would drive it and use it as normal but make sure to kick it down at least a couple of times until that fuel was gone.
I have had this greatly extend the number of miles I can go before my check engine light pops on.
I don't know that it'll actually fix the problem long term but it will take a light that comes on every second or third trip and that's just because the trips weren't long enough to get through all the tests to pop the light but it was pending earlier, and it will turn that into like going a month or even 2 to 3 months before the light pops on.
I have an older one right now that pops one of the codes I think 0430 and I just don't worry about it and sometimes just leave the scan tool hooked up and reset it when it pops on if I'm feeling annoyed by it that day.
The code does nothing as far as the way my car, or most cars run for that matter.
People, and the industry will lead you to believe that anytime a light is on you're getting poor fuel mileage or something like that but in many almost most cases this is not true.

 

[TobyU]

I have the PO430 code on my 2014 (driver side bank 2). The vehicle runs fine. I have a scan tool with graphing capabilities and with the help of the linked video, I was able to determine the cat on bank 2 just isn't doing its job. My downstream O2 sensor was mimicking the front O2 sensor. which it should not do (see video). But since the vehicle runs fine I might not do anything about it for a while. The temps on the cats were also around 700 and there is no loose substrate. A couple of years ago I had some misfiring going on and this might have contributed to the bank 2 cat demise, not sure.
https://youtu.be/xLyytQD7njw

That's exactly it! I've seen this so many times and if you read my other post I comment on this too.
An ignition misfire for only a day or two of driving can injure a cat enough to make it lazy or weak.
Try cleaning yours with high percentage isopropyl alcohol or three bottles of that heet fuel treatment and you will probably see the light pop on less frequently.

 

[TobyU]

Thank you for reply, I will check out the video you linked.
I have a BlueDriver OBDII scanner, but it says that I can only transmit live data from the upstream sensors, and it says "not supported by this vehicle", when I go to try and read live data from the downstream sensors.
I may have to bring it to a shop and have them read the voltage for me.

I had a misfire back in November 2019, but it didn't last for long and was very intermittent. I am not considering this misfire as a cause for these codes.

I am going to try and reset the fuel trims and see if it fixes this problem, the vehicle was sitting for quite some time, and then driven below 10mph for only a couple of months, and a lot of idle hours...

It almost certainly is from the misfire as that's what always causes this.
Have you gotten all the old gas out of there and added enough that you've driven all the old stuff out yet?
That can make the problem more apparent also and how are those long-term and short-term fuel trims looking.
I had a Town Car once with a 4.6 that had some vacuum leaks causing the short-term fuel trims to be a lot higher than they should be and that of course doesn't help anything.
You can get into a mental exercise about whether a vacuum leak causing a lean condition is better or worse for what the oxygen sensor senses after the converter even if the converter is weak but that's kind of a moot point because the car is trying to adjust everything as quickly as you see the result or as quickly as the vacuum leak takes its effect so at the end of the day it could be dumping more fuel than it should because of the vacuum leak so it starts out being lean but it ends up being rich and it could go back and forth so you just can't bank on any of that..
Funny things happen in real world use versus the way things are supposed to happen. Lol

 

[stilbo]

I’ve had a P0420 code on my 2015 Expedition and 2015 Explorer…
I utilized my Foxwell analyzer graphing tool to compare bank 1 and bank 2 O2 voltages and noticed a difference in waveforms bank to bank so I elected to go the most thrifty route first by replacing the bank 1 O2 sensors in both vehicles and resetting the DTC’s.
Both vehicles have not thrown that code in more than 3,000 miles to date.
Being that the Explorer only had 47,000 miles when the sensor failed and the Expedition sensor was apparently the same part number, I got the impression that there were some junk Motorcraft O2 sensors in the manufacturing mix.
I’ve read numerous reports of dealership service departments and independent shops replacing the catalytic converters at a very expensive price only to have the CEL pop up with a P0240 code again.

 

[TobyU]

I’ve had a P0420 code on my 2015 Expedition and 2015 Explorer…
I utilized my Foxwell analyzer graphing tool to compare bank 1 and bank 2 O2 voltages and noticed a difference in waveforms bank to bank so I elected to go the most thrifty route first by replacing the bank 1 O2 sensors in both vehicles and resetting the DTC’s.
Both vehicles have not thrown that code in more than 3,000 miles to date.
Being that the Explorer only had 47,000 miles when the sensor failed and the Expedition sensor was apparently the same part number, I got the impression that there were some junk Motorcraft O2 sensors in the manufacturing mix.
I’ve read numerous reports of dealership service departments and independent shops replacing the catalytic converters at a very expensive price only to have the CEL pop up with a P0240 code again.

That's what I mentioned in my previous post. Most of the time it is a lazy converter due to an ignition misfire being driven too long but as I said it's hard for the average person with the most common scan tools to really tell if the O2 sensors are doing their job or not so that's why I said occasionally it can be that but over the course of the years so many people have replaced O2 sensors that were just doing their job and reporting the lazy converter so they just wasted their money and time.
With the average scan tool even the slightly better ones all you see is a quick readout of the millivolts and it's switching back and forth so you can barely tell what the peak High and peak low is because it switches so quickly and you can see how fast it switches but that's not nearly as good as higher in sophisticated graphing stuff like you said you used.
I'm glad yours was just an O2 sensor and it hasn't come back but about 9.3 times out of 10 when someone has this code and replaces the O2 sensors, they still get the code quickly.

 

[stilbo]

Interestingly I was also able to stave off the P0240 code in the Explorer for more than 1,000 miles on two occasions by running the fuel level to near empty, filling it with ethanol free gasoline and pouring a large bottle of Chevron Techron fuel system cleaner into the tank.

My Foxwell Analyzer has an ethanol monitoring function that works so long as the vehicle has the ability to detect the ethanol content and the Explorer had been fed 16% ethanol in two fill ups prior to the P0240 code.

Not sure if that would have had any effect on the O2 sensors but I had thought about the alcohol causing corrosion or contamination of fuel injectors and subsequent reaction of the O2 sensors….

But again, just replacing the O2 sensors seems to have been the fix..

They cost anywhere from $39-$110 at Rock Auto and definitely worth a try especially if you’re capable of doing the job yourself.

 

[stilbo]

One more kernel of thought….
If an injector were to have been contaminated to the extent that it would not close sufficiently after the intake cycle and allow fuel to enter the cylinder during an exhaust cycle, backfiring would be a result. And even if said condition is intermittent at most, if repeated often enough the ECM would see said rich condition via the O2 sensor and that can be thought to be a failing catalyst.