9 Solutions to Fix P0420 - Don't Start Fixing Before Watching This

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Engine Code P0420 Saving Repair Parts:

Engine Code P0420: Catalyst System Efficiency Below Threshold (Bank 1). It indicates that the Catalytic Converter is not functioning efficiently, so the vehicle is increasing the output of harmful pollutants. How to clean the Catalytic converter. Tips and tricks for cleaning a catalytic converter in your car and fixing code P0420.

Method 1: Use a Catalytic Converter Cleaner
1. Get a Catalytic Converter Cleaner
2. Pour into the Gas Tank
3. Run the Engine

Method 2: Wash the Catalytic Converter
1. Remove the Catalytic Converter
2. Get a Bucket with Water & Detergent
3. Soak the Converter for 10 Hours

Method 3: Modify the Oxygen Sensor
1. Remove the Oxygen Sensor
2. Prepare the Components
3. Refit the Components
4. Re-install the Oxygen Sensor

Method 4: Oxygen Sensor Replacement
1. Inspect the Oxygen Sensor
2. Replace the Oxygen Sensor

Method 5: Adjust Spark Plugs
1. Remove the Spark Plug
2. Check the Spark Plug
3. Adjust the Spark Plug

Method 6: Replace Fuel Injectors
1. Inspect the Leaking Fuel Injectors
2. Remove All Fuel Injectors
3. Dip Them All in Gasoline
4. Reinstall the New Fuel Injectors

Method 7: Paste the Exhaust Leaks
1. Inspect and Clean the Leaks
2. Apply the Exhaust Putty
3. Let it Cure for 2-24 Hours

Method 8: Wrap Up the Exhaust Leaks
1. Inspect and Clean the Leaks
2. Activate the Heat Wrap
3. Apply the Heat Wrap
4. Run the Engine for 30 Minutes

Method 9: ECT sensor
1. Inspect the ECT Sensor
2. Replace the ECT Sensor

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0:00 P0420 Intro
1:19 Method 1: Use a Catalytic Converter Cleaner
1:54 Method 2: Wash the Catalytic Converter
2:58 Method 3: Modify the Oxygen Sensor
3:37 Method 4: Oxygen Sensor Replacement
4:40 Method 5: Adjust Spark Plugs
6:07 Method 6: Replace Fuel Injectors
7:28 Method 7: Paste the Exhaust Leaks
8:18 Method 8: Wrap Up the Exhaust Leaks
9:49 Method 9: Replace ECT Sensor

[Johnslist]

Very professional and absolutely thorough. I've been wrestling with P0420 for most of the year and found these ideas individually. It's nice to see them altogether in a very professional presentation. I'm finally ready to order a cat, but I called the manufacturer and he agreed that it was often not the cat - but I've looked at all these others already. So frustrating, mainly because my cat is welded inline so I can't even check it. Alldata points to bad cat, but I keep thinking it's something else.

[madeleyinc]

P0420 on my vehicle turned out to be a vacuum leak in a vacuum hose from the intake manifold.

[TheWilferch]

Another possible reason for getting PO420 code that is not mentioned....an exhaust leak somewhere that screws up the "comparison" signal between the upstream and downstream O2 them to say the cat is working below efficiency. One place to look beside obvious rust holes in the piping is the first flange gasket at the exhaust manifold. If this leaks, it screws up the readings and causes the code.

[GODMODE]

How much will the dealership or a local garage charge for diagnostic and fix? Everytime I go to one with a check engine light, they are magically able to charge upwards of $1000 for a fix, no matter what the issue is.

[FRLNCR]

Never use the spark plug gapper itself against the electrode to bend the ground tab as shown in this video. Could easily damage the electrode.
Bend the ground tab from the back of it with a proper gap adjustment tool or carefully with needle nose pliers if the tool isn't available.
Use a wire loop type feeler gauge on exotic metal plugs for proper gap setting to prevent damage.

Most wire loop feeler gauges have a ground tab bender included.

[ShootingAnalysis]

Very comprehensive diagnosis and solution! I ended paying the $16 bluetooth kit shipping though I already have an ODB2 scanner.

[benk]

Got a 2004 Toyota Highlander with p0420 code. Took it to a shop and they tested o2 sensors - both are good. But I have no symptoms of a bad cat other than the code itself.

[billyguadarrama]

Very helpful video 🙌. Appreciate the knowledge being passed on.

[ShootingAnalysis]

My 2014 Ford Explorer Police Interceptor 3.7L was reading P0420 P0430, and also pending codes for them. Found hot air flow from a leaking gasket after the catalytic converter to the muffler. Replaced the gasket, weld the cracks between muffler and pipe. Codes are gone, waiting for sensors to be ready again.

[chaseboy]

Carbon build up in the engine can also trigger the code as I own a 2014 Jeep Grand Cherokee Laredo I used Seafoam Intake Cleaner and after it blew all the carbon out the check engine light turned off and never came back on

[ubaldogonzalez]

It is a great way to help me understand the P0420 on my Dodge. However, if you eliminate the music from the video the information will be projected much clearly.

[ramonmota]

Would it erase the freeze frame codes too

[nicolasdakota]

Very useful video and absolutely professional made 👍 it.thank you

[rodmad]

Thank you for the great video and very specific checks for this issue. I have a 2009 chevy cobalt with a new cat converter but i keep getting the 0420 code. I have replaced everything but i have not tried the O2 spacer. Ill give it a shot and report back. Thanks!

[favorites]

This was great thank you I'm going to subscribe very easy to understand

[Brettdyt]

Method #3 is illegal in most states. The car's emissions system has been modified. The sensor no longer has a steady stream of exhaust to monitor and the car will not pass emissions or be legal to operate.

[GosWardHen]

Enjoyable & really good informative video. Mine us showing the P0420 error, so its gping to be interesting. Thanks.

[desertwaterdemon]

Just did the vacuum bubble test and found a leak on the catalytic converter. Might have to replace it?

[pointnemo]

I really enjoyed watching your videos, very useful. I have lexus is250 2009 and I can sense rotten eggs smell when I drive hard or speed up quickly. What are the problems?

[mackblue]

I have a 2007 nissan altima with 214k miles and it's showing the same code p0420 i haven't use the catalytic cleaner yet but i'm going to try that next to see if i can pass inspection. My code reader was throwing a bank 1 sensor not ready so hopefully this helps.