Before getting started with any repairs, you’ll need to properly diagnose the P0420 code. Most service professionals will use an OBD-II scanner to retrieve the particular code the Power Control Module (PCM) is showing. If the voltage of the downstream oxygen sensor decreases and fluctuates like the upstream oxygen sensor, this is a certain indication that the oxygen levels are too high and the PCM will throw the P0420 code.
However, if there aren’t any visible issues with the upstream and downstream oxygen readings, the mechanic will then check engine misfires, ignition problems and even the fuel system to check for any malfunctions. The mechanic may also check the rear O2 sensor to gauge any excess wear or damage on the part.
An experienced professional will test drive the vehicle and monitor the freeze-frame data. This allows them to determine whether the rear O2 sensor is working properly. Finally, we also suggest updating the PCM to the latest version just in case there’s something wrong with it. It’s not uncommon that an out-of-date PCM is behind your vehicle’s issues.
FAQs
This code suggests that the oxygen levels are below the desired threshold (Bank 1), which most often results from problems with your car's exhaust or fuel systems. It can sometimes be tricky to diagnose. The catalytic converter is a component of the vehicle's exhaust system.
What is the most common cause for a P0420 code? ›
A common emissions code seen in the field, a P0420 trouble code indicates that the catalytic converter isn't functioning efficiently. To work at peak efficiency, the emissions or feed gases entering the catalytic converter need to be perfectly balanced and not excessively elevated.
Where is P0420 Bank 1 located? ›
It indicates that the exhaust system's oxygen levels are below the required threshold in Bank 1, which can damage the engine's exhaust and fuel system. Bank 1 refers to the side of the engine that houses the number one cylinder. The opposite side of the engine is Bank 2.
Can I still drive my car with P0420 code? ›
How Serious Is the P0420 Code? Driving your car with the P0420 code will only lead to further damage to the catalytic converter.
How do I unclog a catalytic converter? ›
Soaking: One method to try is submerging and soaking the catalytic converter in a soapy water solution. A dedicated oil or degreaser product will probably work best, though you might also try dish soap. Add your cleaner to a sufficiently large bucket of water where the converter can fit.
How much does it cost to fix a P0420 code? ›
Estimated Cost of Repair for a P0420 Code
The average cost of repairing a catalytic converter can range from $1,000 to $2,500. A catalytic converter replacement starts around $2,000, O2 sensor replacement can cost $150 to $500.
Is there a catalytic converter cleaner that actually works? ›
Fortunately, a product like the Rislone Cat Complete Fuel, Exhaust and Emissions System Cleaner 16.9oz can help switch that light off and clean out the soot, carbon build-up, and residue in your fuel system.
Will the P0420 code clear itself? ›
Does P0420 Clear Itself? Once you've rectified the root cause of the issue, you can go about clearing the code. If you don't have access to an ODB II reader to clear the codes, it should clear itself within a couple of drives.
How do I know if I have a bad O2 sensor or catalytic converter? ›
To check if it's a clogged cat versus a bad oxygen sensor (when you don't have a check engine light), grab a vacuum gauge. Connect the gauge to an intake manifold vacuum line. Start the engine, let it idle, and check the reading on the gauge.
What happens if I ignore P0420? ›
What happens if I ignore P0420? Though you can drive with this error code, we recommend you not do it for a long period. Ignoring this engine code can cause higher emissions, decreased fuel efficiency, and possibly substantial damage to the car's catalytic converter or engine.
That could be due to an excessively rich fuel mixture, a leaking fuel injector, or a compression/engine timing issue that won't burn the fuel correctly. If you're seeing correct readings from the oxygen sensors, try playing around with the fuel mixtures and see if the engine computer is able to compensate correctly.
How to fix O2 sensor code bank 1? ›
How Do I Fix Trouble Code P0130? The majority of the time, the oxygen sensor is bad when this error pops up. If you are running an O2 sensor past its due date for replacement according to your owner's manual, it's a safe bet to start with a replacement and see if it's enough to resolve the problem.
Will a P0420 code clear itself? ›
Does P0420 Clear Itself? Once you've rectified the root cause of the issue, you can go about clearing the code. If you don't have access to an ODB II reader to clear the codes, it should clear itself within a couple of drives.
How long does it take for P0420 to reset? ›
After around 10-20 cycles, the reset may occur automatically. A cycle is a phase in which you turn on and off the ignition. Here's a video to help you understand more about the P0420 code: An error occurred.
How to reset catalytic converter monitor? ›
Accelerate to 50 MPH, then decelerate to less than 6 MPH without touching the brake. Repeat at least 5 times. Once again, I had to go out and make new friends on the road, but the monitor passed. There was nothing wrong with the car.
Why does the P0420 keep coming on? ›
That could be due to an excessively rich fuel mixture, a leaking fuel injector, or a compression/engine timing issue that won't burn the fuel correctly. If you're seeing correct readings from the oxygen sensors, try playing around with the fuel mixtures and see if the engine computer is able to compensate correctly.
