Check Engine Light Code P0420

D

daviddep

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Check Engine Light intermittently comes on and off, for almost a year.


Done the following:
1. Replaced Bank 1 Exhaust Catalytic converter manifold. (with Used one, from reputable Ebay dealer, who says it is good working order.)
2. Replaced Up& Down Stream Bank 1 O2 sensors.
3. Ran cataclean in fuel system.

Same results, but Check Engline Light stays off longer since doing the above. got 400 miles before light came back on after replacing O2 sensors.Now its Back on again. It will go out again, and repeat the issue. ON for awhile, OFF for awhile.

Can anyone confirm: If the Catalytic Converter is truly the cause, wouldn't the Check Engine light stay on constantly? As my issue is Intermittent P0420 code. (Catalyst System Efficiency Below Threshold Bank 1.)

I dont want to be replacing the Cat with a New one if we Don't have too.

Other possible reasons:
Air Fuel Ratio Sensor?

Mass Air Flow Sensor MAF?

Reset Engine Control Module (ECM w/C1201, C1223) ?

Exhause Leaks? Bad Exhaust Gaskets?

Thanks!
 
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Don't know if this helps but I read recently some exhaust gasket near the converter was replaced and that fixed the check engine code, seems it was leaking in just enough fresh air for the code to set.
 
Try getting a laser thermometer and then running the truck so the Cat's are nice and hot so they can do their job. Get under the truck and try checking temps for inlet and for outlet of the Cat's. I tested the cats with my thermometer and the one under the drivers seat had a high inlet temp but the outlet was only like 210 degrees. I cant remember what exactly the inlet temp was but it was a couple hundred degree difference. So I suspect the Cat is plugging off and therefore not heating up the exhaust like it should. Hope this helps.
 
Supersonic said:
Don't know if this helps but I read recently some exhaust gasket near the converter was replaced and that fixed the check engine code, seems it was leaking in just enough fresh air for the code to set.
Click to expand...

we replaced the gaskets when replaced the Cat... Thanks
 
zonianbrat said:
Try getting a laser thermometer and then running the truck so the Cat's are nice and hot so they can do their job. Get under the truck and try checking temps for inlet and for outlet of the Cat's. I tested the cats with my thermometer and the one under the drivers seat had a high inlet temp but the outlet was only like 210 degrees. I cant remember what exactly the inlet temp was but it was a couple hundred degree difference. So I suspect the Cat is plugging off and therefore not heating up the exhaust like it should. Hope this helps.
Click to expand...

I measured the Replaced Bank 1 Cat downstream temperature, versus the Bank 2 Cat. The replaced Cat was 50-75 degrees cooler. So that tells me that the Bank 1 Cat is doing it job... It must be something else.. I was thinking to replace the Bank 1 with a NEW OEM, but its not gonna help I dont think. I'm going to run Cataclean through it for several tankfuls... Could be dirty fuel system.. etc.

Thanks for the Tip. I've been meaning to do that...
 
So by replaced cat you mean the original cat was running 50 to 75 degrees cooler correct? Sorry it's 5:30 am and I just worked all night so my mind is fuzzy. Either way sounds like you are on the correct track by troubleshooting and eliminating things one by one. Emission problems suck as it is such a generic code that could be so many things. Good luck and keep us posted on what you find.
 
zonianbrat said:
So by replaced cat you mean the original cat was running 50 to 75 degrees cooler correct? Sorry it's 5:30 am and I just worked all night so my mind is fuzzy. Either way sounds like you are on the correct track by troubleshooting and eliminating things one by one. Emission problems suck as it is such a generic code that could be so many things. Good luck and keep us posted on what you find.
Click to expand...

Not compared to original Bank 1 Cat.... never took the temperature reading on the original..

Did temperature reading on the new used cat and comparing it to do existing bank 2 cat.. so the replacement cat is running significantly cooler then the bank 2 cat...

so that tells me that the new used cat is doing its job..

it should not be triggering an error code...

If anything the bank 2 Cat should be causing a code...but its not...





Com
 
Code: P0420

2004 T4R SR5 V6 4WD, Miles:155k

Some back ground about my current code P0420:

Driving to work, CEL started flashing, VSC TRAC & OFF lights came on. Car is running rough/sputtering, but driveable. Was maybe 5 miles from work, so drove it there to the shop next door. They ended up replacing a coilpack/spark plug on cylinder 5. I picked it up and before I was 100 yards away both VSC lights turn back on. They scan if to find out it needed to be calibrated (using Snap On Scan Tool), they complete, clear the code and all good.

24 hours later, CEL (not flashing) & both VSC lights are back on. This time I am told code: P0420 and told its related to my catalytic converter. They cleared the code but it came back on within 20 miles.

Any thoughts anyone?

Car runs great btw and not sure what are the best options. I have searched via Google for some solution (cost saving ones as its a 14 year old car) and came across an 02 sensor spacer mod, any thoughts? Any suggestions? I mention the spacer because I don't need to be emission compliant but don't want to mess up my car either.

Any and all advice is appreciated.

Thanks.
 
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Hate to say it but nearly always this code means what it says absent any other codes or drivability issues. This code trips when the delta between pre-cat o2 sensor and the post-cat sensor falls below a certain threshold. The truck runs great because everything is peachy all the way to the cat itself. Just went through this with my son-in-laws Pathfinder.

Just saw you mentioned the spacer mod...... if you don't need to pass a smog test then that will probably work. It wouldn't here because it would fail a visible inspection.
 
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yeah I live in VA and my car is registered in a county that does not require emissions either. So to be honest, getting the CEL to disappear is just for peace of mind and knowing that when I do see it again it's for another issue that I need to address besides this emissions/smog one.

get it?

thanks for your post and as i really appreciate it.

i do have 1 more question if you if have any insight...which O2 sensor do you think I need to place the spacer or should I do it for both of them to remove all risk of getting a reading the will trigger a CEL due to anything related to my CAT.

Thanks in advance.
 
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Bank 1 is whichever side has the #1 cylinder, a p0430 code is for bank 2. If you have easy access might as well do both, the spacers are only $10 apiece.
 
Where did you find them for $10?

I found them on Ebay for $15 to $38 (each), I don’t have the equipment to drill so I need a simple solution.

$38: O2 OXYGEN SENSOR SPACER NEW DOWNSTREAM FOR TOYOTA TACOMA 2000-2004 https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/262924344509

$15: O2 OXYGEN SPACER SENSOR BUNG EXTENSION 45 DEGREES 02 OBD2 https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/263077152480

If you know of a better place to find one that would be the best fit, I am all ears!

Thank you!
 
you're awesome and thanks so much.

so there are 4 sensors all together...from what i just learned. by no means am i anything close to being a mechanic.

so would a spacer be something i'd use on all 4 or which ones specifically?

thanks again my friend.
 
Just the 2 post-cat o2 sensors..... your 2 closest to the engine are fine and working properly. Hell, all of them are working properly for that matter, its your cat thats weak. Still working but weak. The pre-cat o2 reads the exhaust gas coming from the engine into the cat, the downstream sensor measures the gas coming out of the cat and your ECU compares the 2 readings. If its not reading a high enough difference it figures the cat is not efficient enough and pops on the code.
 
Thank you for taking the time to answer my questions! So appreciated!

Sending some good karma your way!

Have a great weekend!
 
Seeing as how this code popped in conjunction with rough running and a bad plug, it might be worth getting your injectors checked. A leaky injector would easily foul a plug and quickly nuke the cat.
 
One of the most useful tools I've found from my BMW days is OBD Fusion. It's an app that runs on iphone or android. Costs about $4. You need an OBD bluetooth or wifi dongle but they are $5 on ebay as well. With this tool you can set up data logging. You can then monitor many parameters of the engine like O2 sensor outputs, fuel trims, temps, rpm, speed, fuel pressure, and more others than I can remember. These are placed in a log file while you drive that you can then examine later for clues as to what's wrong. It will also do the usual OBD stuff like read/clear codes and real time dashboard displays but the data logging is what's so useful.
 
I was throwing the same code. Just had my exhaust shop cut off my cats and install high flow cats. Worked and the light is still off. Cost $300 total for 2 new high flow cats, and labor
 
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