Showing articles & questions for topic
P0420

Related articles

P0420 OBD-II Trouble Code: Catalyst System Efficiency Below Threshold (Bank 1)
P0420 code definition Catalyst System Efficiency Below Threshold (Bank 1) What the P0420 code means The catalytic converter pulls in the pollutants that are expelled by the cylinders and uses oxygen...

Related questions

Question
P0420 code after idle relearn
Hello. P0420 is the code for catalyst efficiency below the correct threshold for bank 1. If you do not believe the catalytic converters are the issue, then the first thing I would do is check the bank 1 oxygen sensors....
Question
How to get more horsepower without the check engine light and still still pass smog
Coming from a realistic point of view, I'd say that unless you were to pull your motor and completely rebuild it, from pan to fuel injection, you might want to consider NOT adding components for horsepower. With over 200,000 miles,...
Question
The engine light is on and the code is P0420 - Catalyst System Efficiency Below Threshold Bank . What part do I need to fix it?
While a number of things like a faulty oxygen sensor or exhaust leak can cause fault code P0420 to be set, the most common fault is the catalytic converter itself. However, as a replacement can be very expensive, your best...
Question
Check Engine Light is on - trouble code P0420
As you may know, trouble code P0420 relates to the inefficiency of the catalyst system, which detects the presence of oxygen in the exhaust gases. This can be caused by failing O2 sensors that need to be replaced. This can...
Question
Check Engine Light on - P2187 and P0420 codes
Hello. If I understand correctly, when you say "catless downpipe," you mean that you have installed a pipe without a catalytic converter. If that is the case, you are always going to have the code for catalyst efficiency. The...
Question
Po420 bank1
Hello Tom. P0420 is the Catalyst System Efficiency Below Threshold (Bank 1) code. While there are a multitude of components that can cause this code, the general concept is that your catalytic converter is not working properly. If you suspect...
Question
P0420 code and engine is not starting.
Hi there. The p0420 code means that the catalytic converter is below threshold and is not functioning correctly. This code comes up when the catalytic converter can no longer burn off any fuel in the exhaust system. Take a raytech...
Question
P0420 - CATALYST B1 DETERIORATION
Hello - it is possible the 2 problems are related, but likely only over a long period of time. The P0420 code is a "low efficiency catalytic converter" for Bank2 - which include cylinder 1. And yes, that warning is...
Question
Misfire and P0420
Hello - the P0420 and the inconsistent waveform for the post-cat O2 sensor might be related to your failing intake manifold gasket issue. If tiny droplets of coolant are being sucked into the engine - one failure mode for this...
Question
My car shows a P0420 code and the engine coolant temperature reading (via torque pro app and elm327 Bluetooth reader) stayed at 84.2 degrees
Hi there - "boundary measured engine temperature," or the lowest temp reading a sensor can transmit, can be different based on each temperature sensor. The issue here is what is the true engine temperature? Is the thermostat getting the engine...
Question
p0303, p1313, p0420. codes come up. no flashing and now signs. what do I do?
Hi there. Sounds like there are a few things going on. First the code P1313 means that the timing chain has jumped a tooth making the camshaft and crankshaft out of sync. The chain tensioner may need replaced if it...
Question
p0420
A vehicle with 182,000 miles is likely due for a catalytic converter. Most of the time it does mean you need a new catalytic converter. But there are a couple of other things that are prudent to take a look...
Question
P0420 P0430 trouble codes
Hello. Thanks for writing in. The universal oxygen sensors, a bad connection, or a bad catalytic converter can all be the cause of the codes. If you can you access to a known good oxygen sensor and test it in...
Question
Code P0420 shows on the dash of my 2005 Acura MDX
Acura did have a tech bulletin released in September 2011 regarding fault P0420 and a possible software update that may rectify this situation. You can try contacting your local Acura dealer service department or Acura Customer service to see if...
Question
05 Nissan Frontier has a code of p1283 and p0420. Why are these codes stored?
Hi there. The code p0420 is present for the O2 sensor behind the catalytic converter has detected the air fuel ratio is not within the limits. The code p1283 is present for the air fuel ratio sensor is registering a...
Question
I took my car to Advance Auto and them do a check engine light diagnostic test and the code is C0245
Hello. Thanks for writing in. You may have two separate issues going on at once. The speed sensor code is likely due to sensor failure, or a bad connection. In the case of a bad connection, a good visual inspection...
Question
2004 Nissan Altima- Won't move when the code reads p0420 on the scanner. Did my transmission go? Is it my catalytic converter like code said?
Hi there. The code P0420 means that the catalytic converter is below threshold and cannot burn off any emissions in the exhaust stream. The O2 sensors have pickup this fault and put the engine into limp mode. As for the...
Question
My car shows trouble codes P0133 and P0420
Hi there: It appears as if you've got a lot of miscommunication going on with your mechanic. Here are a few basics. First, anytime an error code is triggered, such as the P0133 OBD-II code the issue needs to be...
Question
My engine is about to kill itself.
If the vehicle transmission has entered limp mode and the engine is really misfiring, these faults have to be diagnosed separately. The engine misfiring should be dealt with first. Typically, the engine is scoped to look at secondary firing patterns...
Question
Code P0420. Need to replace catalytic converter.
Hi there. The code P0420 is coming up for the Downstream Oxygen sensor has picked up an abnormal reading and is saying that the catalytic converter is below threshold. There could be a misfire on the engine, leaking injector, ignition...

Need a mechanic?

Our certified mobile mechanics make house calls in over 700 U.S. cities. Fast, free online quotes for your car repair.

Get a quote

Post a question and get free advice from our certified mechanics.


Ask a question