Check engine light code P0420
my check engine light came on after I filled gas. I got the code read and it was the code P0420 for catalytic converter. However, after I drove it a couple times the light went off. I filled gas, it went back on and as before after driving a couple times it went off. Why would it be going on and off if there was a problem?
My car has 65000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
You may have a purge valve that is leaking and causing excessive fumes to enter the intake manifold during the refuel process. When you start the vehicle, the excessive rich mixture may be causing the catalyst to overheat which will trigger the P0420 code. This will happen if, after a couple of starts, the computer does not see a problem and clears the code.
I’d recommend seeking some assistance from a certified mechanic who can diagnose your Check Engine Light first hand and fix the problem accordingly.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
Code P0420 indicates that the catalytic converter is not functioning efficiently, therefore increasing the output of harmful pollutants by the vehicle.
The P0420 code signals a low catalyst system efficiency. 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.
A P0420 code is set when the upstream sensor and the downstream oxygen sensor sense the catalytic converter is not doing its job. Basically, the amount of oxygen going into the converter is not being burned, and it detects it through the downstream sensor.
Yes, you may be able to fix P0420 yourself. Depending on the cause of the code, the diagnosis and the repair might be simple or might be very difficult to do at home. You might need access to a welder if you need to patch an exhaust leak. You might also cause more damage trying to repair your problem.
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.
Because there are no driveability symptoms associated with the P0420 trouble code, it is not considered serious or dangerous to the driver. However, if the code is not addressed in a timely manner, the catalytic converter could be seriously damaged.
P0420 typically means that a converter has worn out or degraded—not obstructed or clogged. But if the case is the latter, it can lead to engine performance problems, such as a lack of power, rough idling, and stalling, which are some of the common signs of a clogged catalytic converter.
P0420 means a catalytic converter problem affecting its efficiency or a problem with the oxygen sensors. So yes, it could be a bad plug which is allowing unburnt fuel to enter the cat and eventually damaging it.
The code P0420 can be caused by the catalyst, O2 sensors before and after the catalyst. If both O2 sensors and catalyst was replaced then you may have an exhaust leak at the manifold or pipes.
If the engine is burning oil, which sounds like yours does, this can damage the catalytic converter, which can result in the P0420 DTC.
A P0420 code indicates a malfuction in your Catalytic Converter Efficiency Test due to a failing catalytic converter. However, it can also mean something else such as; Bad O2 sensor (either upstream or downstream), either the heater circuit or a stuck value. An exhaust leak which may fool the O2 sensors.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
While driving on freeway truck goes into a limp mode, and the check engine light, abs light, parking break light, service brake
ANSWER : It is possible that you could be having an issue with your powertrain control module. This is somewhat of a common problem on many GM vehicles. I would recommend having your vehicle inspected by the dealership to determine if the powertrain control module is functioning properly. If not, a reflash of the powertrain control module may resolve the issue but often times it must be replaced.
Read Full Q/A … : Check engine light code P0420
p0011 code,check engine light one, changed bank 1 vvt solenoid and check engine light still on?
ANSWER : The P0011 code is typically caused by oil issues with the car. I would particularly make sure the engine oil level is not low. The VVT solenoid relies on proper oil levels to do their job. If they don’t have enough oil, they won’t work. You can have a mobile technician from YourMechanic visit your home or office to inspect the Check Engine Light for you. If you follow through with a repair with us you will be reimbursed for the cost of inspection.
Read Full Q/A … : Check engine light code P0420
P2196 OBD-II Trouble Code. came and went in 24 hours. 4 starts.
ANSWER : If the mechanic tested the output (functioning) of the oxygen sensor, especially according to the protocol at this link and found that the sensor was non functioning at that time, what you might be experiencing is a "failing" oxygen sensor and so the latest instance of Code P2196 might be explained by that. A complexity though is Code P2196 has many causes other than a failing oxygen sensor including: a faulty fuel pressure regulator; MAF (Mass Air Flow) sensor; ECT(Engine Coolant Temperature) sensor or damaged ECT wiring; leaking or stuck open fuel injector or injectors; and spark plugs and/or coil pack. Basically, if the Code (P2196) recurs, the oxygen sensor output can be re-tested but the mechanic will hopefully be aware of all these other possible causes of that Code setting. If the Code recurs, you can request a check engine light diagnostic and a certified Mechanic, dispatched by YourMechanic right to your location, will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
Read Full Q/A … : Check engine light code P0420
I have a 2007 dodge ram 1500. Check engine light was on code came up as alternator. Replaced it and the check engine light is stil
ANSWER : Hi there. When an error code is created, it is often stored in the ECU until it is cleared by a professional mechanic during a check engine light inspection. It is possible that this is the source of your error light, especially if you are not having any further problems starting your vehicle.
Read Full Q/A … : Check engine light code P0420
Check engine light refuses to go off after engine replaced
ANSWER : Hello there, you have a long series of issues going on with your 2013 Hyundai Sonata. If you keep getting a repeating oil light on than there is likely a fault in that system.
Since this fault has lasted after the engine was replaced it could be a oil pressure sensor, wiring harness fault, ECU fault, oil pump, oil strainer clogged, or low oil pressure.
To diagnose this issue properly you need a complete vehicle inspection to start from square one and identify the root cause of all this.
Read Full Q/A … : Check engine light code P0420
check engine light O2 sensor already replaced same codes still popping up after replacing old O2 sensor
ANSWER : Hi there. What you received from the parts store was a code retrieval, not a diagnostic. The codes are set when a fault is detected against normal operating parameter. The computer does not know what caused the fault, only that the fault meets the criteria for this code to set. There could be a problem in the wire harness, converter, or the ECM. The code and data are needed to properly assess the direction that a diagnosis needs. I strongly suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.
Read Full Q/A … : Check engine light code P0420
2006 Ford Mustang has check engine light on
ANSWER : There are countless potential causes for your illuminated check engine light. The mechanic manually turned off the light, but it came back on because the problem has not been fixed. The first place to start is retrieval of the stored diagnostic trouble codes (DTCs). These codes serve as a starting point for any further diagnostics a mechanic may perform. Codes will be stored anytime the check engine light is on. Since the first mechanic was unable to fix your concern, I recommend giving the professionals at YourMechanic a call. We offer expert check engine light diagnosis and repair.
Read Full Q/A … : Check engine light code P0420
Car started to slow down and then the check engine light, battery, and engine oil light came on. What could cause this?
ANSWER : Hi there. It is possible that the battery cable came loose or the wires to the oil pressure sensor has came loose or failed. Check the battery cables and make sure that the terminals are tight and clean. Check the wires to the oil pressure sensor and make sure that they are connected and not broken. If everything looks good, then the oil pressure sensor may have failed. Plus, check the computer for codes and see what is stored. This will lead you to the part that could have failed. I recommend replacing the oil pressure sensor then checking to see if the lights will go out. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from Your Mechanic, that can assist you with the warning lights that came on.
Read Full Q/A … : Check engine light code P0420
