Causes and Fixes Chevrolet P0420 Code: Catalyst System Low Efficiency Bank 1

[@docwilliams9801]

Video was thorough AF! Thank you for this!

[@FNEIN]

bro out here doing gods work.

[@polarbear2469]

I had the same issues with a 2017 Chevy Tahoe, the cat was throwing the code because the vehicle was running rich. The thermostat was opening @ 163F but should open @ 194F.

[@SwagAli593]

Did you fix it changing the thermostat?

[@KourtneyWebb]

I have a 2017 Chevy Tahoe as well, and I’m getting this same message. Did you find out if it was the cat?

[@kiddkurama4155]

How did you fix the issue? Same year and all

[@mo548]

any luck ?

[@SlaneVintageModern]

I just got the code. 2017 Tahoe that I just did the lifters, injections, cam.

[@mrashad219]

Wow I gotta watch it again with a notebook

[@rdrodd1799]

Could a misfire cause this to throw a P0420 code? Thank you.

[@datmanz5890]

Yes, I have a 2013 tahoe with the same code with brand new cats. I have a random misfire but not a dead misfire. Check your fuel injectors, and vacuum leaks.

[@rdrodd1799]

Thank you.

[@cherieunsworth1922]

I had my catalytic converter changed 2 years ago in my 2005 Buick LeSabre. Over this past summer when it was really hot the Service Engine Soon light came on, once the temperature got a little lower it went off. This past week it came back on but I have been driving alot more than usual and I have been using my heater because, for me, it's been cold. P0420 is the code that came up. The car is running as good as an almost 20 year old car can. Could it just be the sensors or should I worry about having to replace the catalytic converter again (which I definitely can not afford)?

[@HVAC_Mechanic]

The 02 sensors would need to be tested to see if they have failed. Since the Cat was recently replaced, and if the sensors are good, I would run Cata Clean and see if it clears.

[@sergeantseven4240]

Getting this code after I replaced the catalytic converters and all of the O2 sensors and the MAF sensor, MAP sensor, and replaced the throttle body gasket and cleaned the intake. Getting bad mpg and not a lot of engine power. I'm at my wits end with this truck... The only code I have now is this code on the bank 2. I have a lifter ticking noise in the passenger side rear cylinder and I'm starting to wonder if there is an issue with the valve train causing this. I have 165k miles on the truck and have yet to replace the o ring on the oil pickup. I'm curious if doing that will clear up the lifter tick and get the engine running correctly. Truck has all new exhaust system, shorty headers, new plugs, plug wires, and coils. I have yet to tear down the top end and do new gaskets and seals but I'm scared of what I might find. I also have not done a compression test yet.

[@HVAC_Mechanic]

A P0420 code point to a CAT issue or an O2 sensor. I would loosen up the exhaust bolts on bank-2 at the flange before the CAT, drive around the block and see if engine power comes back. If power comes back there is an issue with the CAT on bank-2.

[@sergeantseven4240]

@HVAC_Mechanic These cats are brand new, though. I bought the Magnaflow cat kit off summit. Is it possible to have a faulty cat out of the box?

[@HVAC_Mechanic]

While not common, they can sometimes be defective. Anything I say is a guess. The components all need to be tested, but I would rule them out as bad. It is also possible that an engine issue is clogging them up.

[@sergeantseven4240]

@HVAC_Mechanic I appreciate any thoughts you provide. Guess I have more digging to do to find the issue. At least now I have reduced the 4 codes I had down to just one code. Previous owner of the truck did not have it professionally serviced and didn't do very good work themselves.

[@OustandingTv]

Any solutions?

[@skitzupshaw7009]

I'm getting 420 & 496 I only have problems starting after fueling up. Sometimes I'n the morning after initial it almost shuts off them idles high before smoothing out

[@HVAC_Mechanic]

Issue after fueling up is a common symptom of a bad vent valve. I made a full video about each of the EVAP components and how to test them. Here is a link. kzbin.info/www/bejne/eWbWZIWuaNydepI

[@flaco6194]

Replaced the one and only catalytic converter on my vehicle as well with the only two O2 sensors, and the code still comes back. Any suggestions?

[@ericpetteway3841]

Just earned a subscription 😮😊😊

[@SlaneVintageModern]

This is interesting. Doubt you will reply but maybe someone else will or will find this info helpful. I rebuilt the top of the engine. Cam, lifters, not the valves but did do the injection. I cleaned the hell out of the engine. So I’m wondering if it started running richer after cleaning it. Maybe the engine was used to using less fuel because it was getting absorbed by the carbon build up and since I removed the carbon, it started to run rich because there was more fuel now. Sounds like my cat is throwing code because it’s clogged because of rich fuel. Did you or any of you other guys rebuild your engine and have this happen 3 months later? I have 140k miles 2017 Tahoe

[@HVAC_Mechanic]

Sometimes after a rebuild the engine does need to be dialed in. I would test the Bank-1 O2 sensors be sure they are good and then test the CAT. If those test good than it likely is running rich.

[@glentreasure2466]

I had a Chevrolet there with nonstop. They told me two shops told me to murder went out. No I told them to pull Bank one sensor to right at the top of the intake. They pulled that off and started right up and spurred like a little kitten.

[@bradt.3555]

What I can't find is what the downstream should read. Upstreams do what they should and are same both banks. Downstream is steady on both but b1 is steady .7-.8, b2 is steady .1-.2, bank 1 gives me the code.

[@JonnyTheKidd.]

would a exhaust leak behind the second senor cause this code i have a leak in the flex pipe about a foot behind the second oxygen sensor

[@HVAC_Mechanic]

Exhaust leaks can cause issues sometimes, but since it is down after the 02 sensors, it probably won't affect it. I would test the sensors and CAT.

[@JasonOllarvia]

I have a question? I have a 2000 Yukon 4wd, would I do the same process to check my o2 sensor for bank 1 and to check my catalytic converter to see if it clogged

[@HVAC_Mechanic]

Yes, it is the same. A P0420 code is the same across manufacturers with the same causes and fixes. There is manufacturer specific OBDII codes, but a P0420 code is not one of them.

[@xavierramirez4346]

Do you a video explaining about a P2097 code?

[@davidlautwein1338]

When I go down the highway pulling an enclosed trailer I have no issues I got plenty of power it don't stink or nothing until I get off the highway then it comes on

[@jimpowell9205]

I have a 2011 Buick Enclave, with this code for bank 1. I’d like to fix it (3.6L engine), but can’t find a drawing of the exhaust system. Any suggestions?

[@vincentgomez4435]

Let me fix it 😂

[@jimpowell9205]

@@vincentgomez4435 ok, are you close to Knoxville TN?

[@vincentgomez4435]

New Mexico

[@humblebuilds9978]

I had this code twice. I have a 21’ silverado 2.7 turbo. I had this code twice and correct if im wrong for doing this or if that is not related to the code. So when i had this code i basically just ran the truck in the highway up to 85 miles n hr and for some reason the check engine would turn off whenever i would turn on the truck again. Did the problem got fixed due to maybe more heat on the catalytic converter. Or should it still be addressed??

[@HVAC_Mechanic]

The catalytic converter might be starting to fail. Catalytic cleaner can be run through it, such as Cata Clean, which may give it more miles.

[@davidlautwein1338]

I have a 1999 Chevy Silverado with a 5.3 I have the issue with bank one Cadillac converter with a 420 code I have plenty of power it runs fine every once in a while it'll come on in town I can pull a trailer going down the highway and it won't come out until I get off the highway

[@HVAC_Mechanic]

The components need to be tested, but the CAT may be starting to fail. I would run Cata Clean or something similar through it and see if it clears.

[@davidlautwein1338]

@@HVAC_Mechanic I did that

[@mo548]

@@davidlautwein1338any luck ?

[@mo548]

⁠​⁠@@davidlautwein1338what is cataclean?

[@jaemajor]

Opinion on cata clean? The Gas tank additives??

[@HVAC_Mechanic]

Cleaners like Cata Clean can work sometimes and in some cases can add some miles to a catalytic converter, especially a vehicle driven only in a city and not at higher speeds.

[@germanjavierjavier7207]

Question how do I know what it’s the code of the catalitic

[@louofm1]

If you don't have a code reader, and you have a check engine light, you can run it up to AutoZone and they will do a basic code check for free

[@aydinaghajani6645]

hi, I have CAMRY 2011 xle, i HAD p0138 code, I toke it to the mechanic and he changed the oxygen sensor, after about 300 mile engine light popped up with the same code and he said I need to change front sensor too, after changing second sensor engine light popped up with P0420 code! could you please advise? what should I do?

[@SuperExain]

Change mechanic 👨🏻‍🔧 😂

[@diegogonzalez6099]

I ​​⁠agree with @@SuperExain. Get your money back, & Change mechanic quick lol

[@diegogonzalez6099]

If you want to do it yourself then next thing to inspect is catalytic converter. There’s a good chance it can be your catalytic converter.

[@rockydavis7448]

P0420, p0440, wont go over 3000 rpm in safe mode, just put on b1s1 b2s1 02 sensors, and used cataclean, has fuel pressure, full tune up like 2m ago.

[@bryan_trades8867]

Did cataclean work?

[@Jellydoughnut459]

I have a new exhaust as of 2 months ago and it's coming up with this P0420 and P0430 Code.

[@decartesmukombo4770]

Can help me that to do that?

[@antoniohernandez5379]

I have a gmc canyon 2009 and I just can't clear the P0420 code. I replaced the catalyc converter but the code came back after 4 weeks. One thing I didn't do was change the oxygen sensor. Can you advise please?

[@HVAC_Mechanic]

I would test the 02 sensor and check for any exhaust leaks. An engine issue can also cause problems, such as a leaky injector, which can clog up the catalytic converter.

[@jasonschilling7632]

What if all 4 colors are different?

[@HVAC_Mechanic]

When that happens, you will need to find a schematic. Sometimes, you can look on eBay for a replacement, find a sensor that has the correct color code, and match it to the plug.

[@omarellis1832]

I put a new catalytic converter in the code can back on

[@danielescobar7618]

Lol you swapped parts without diagnosing the parts that were there. You threw money in the trash if you didn't put an ohmeter on your O2 sensors.

[@HobbyHijack]

@@danielescobar7618that does not mean it is working accurately

[@danielescobar7618]

@@HobbyHijack lol it really does. You leave it on the car, run it, apply voltage from a variable supply and measure voltage drop. You can compare it to your own readings readings on the bench top. It's the same thing those diagnostic tools do plugged into the car, except those use the car's computer to give you the same values and won't tell you if your wiring is pinched or you have a arc-charred connector adding resistance. I do it manually. It's a little more difficult than plugging in, but you get more info about both the sensor AND the state of the harness and ground straps in the vehicle. It's not for everyone.

[@HobbyHijack]

@@danielescobar7618 i think it’s awesome that you just graduated from Lincoln tech however it really does not .

[@ZGDX_Smiling_]

@HVAC_Mechanic I have the P0420 code on my 2011 Chevy Traverse came up first and then many many many months later, I now have a P0300 code, P0301 and P0303. I have watched this video kzbin.info/www/bejne/eanEoKKgZrOonMk "Causes and Fixes Chevrolet P0300 Code: Engine Misfire Detected". I saw all of my catalytic converter on the outer shell seems like it was getting super old, because the engine now has 183,000 miles on it, when I bought it from 151,000. 2022 I know I change all six spark plugs and ignition coils, I kept all of the old ignition coils. I saw your other video saying that a stuffed-up exhaust system will eventually cause other problems. I can change the rear catalytic converter once I buy it and change all the old ignition coils back in and maybe replace the spark plug again to see if all of that works.

[@akaxjugo20]

I have a 2014 Chevy Sonic LTZ 1.4L TurboCharged Hatchback. I've replaced the entire Exhaust system, ive replaced the upstream and downstrean sensors, Ive tried the Cataclean route, ive gotten my cylinders tested and all coming back good, replaced spark plugs and coil pack and The code has been reset afterwhich check engine light keeps coming back. At this point im ready to trash the vehicle. I cant pass emissions and tired of wasting money on this damn car.

[@mikeluky78]

Fuse or relay

[@mexicanochingon5232]

​@@mikeluky78Do you now whichwant

[@mexicanochingon5232]

@GregArt-v9g where are you get the catalytic converter

[@inaday07]

If it drives you can get a paper from dmv to bypass inspection

[@LOLONO666]

cataclean,,forget it

[@MEGARECORDSLLC]

New cat new 02 sensors new plugs new map sensor and still have P0420 code

[@JustinSimmons-hd4pw]

Gotta be ecm computer got confused I bet

[@poltergeizt6856]

Or exhaust leak

[@poltergeizt6856]

Like the exhaust manifolds on these models of vehicles have issues sometimes

[@kingkai9818]

​@@poltergeizt6856 I got everything change including the manifold and I still got p0420

[@joeyoungs8426]

The 2.4L is notorious for cracks in the exhaust manifold. Most times you can smell it coming in the cabin from the HVAC system. You should also check the coolant temp. Once warmed up it should run in the mid to upper 180’s during cooler weather and around the lower 200’s in warmer weather. Wouldn’t hurt to also check fuel trim range and misfire data.

[@majid9117]

Don't spend your time and your money ,you must change the Cat

[@Jaystonishing]

What vehicle and mileage do you have bro? I got a 17 yukon with 60k miles and I find it hard to believe the Cat needs replacing already.. I'm in denial I guess lol

[@jonathanlopez2650]

@@Jaystonishingactually, a catalytic converter is supposed to last around that long in mileage, it’s not exact but around there is when you’ll need a new one. So there ya go

[@lousassle2327]

Would this stop my van from starting

[@HVAC_Mechanic]

It should still start, just not run as well as it should.