Q: Catalyst system efficiency
I am getting code P0420, catalyst system efficiency below threshold.
Recommended Services
| Smoke from engine or exhaust Inspection | $94.99 - $114.99 | Get a Quote |
Hi. There are a few things to check out when receiving this code as it doesn’t always mean the catalytic converter is going bad. The car has multiple oxygen sensors that test how efficient the converter is performing. If the sensors are failing, they will give incorrect readings which will convince the computer that the converter is at fault. Exhaust leaks can also throw off the readings the oxygen sensors get, which will confuse the computer as well. Lastly, the catalytic converter itself may be failing which appears to be a somewhat common issue with the Altimas. You should have a certified technician, such as one from YourMechanic, help you inspect the whole exhaust system to find the cause of the problem.
The statements expressed above are only for informational purposes and should be independently verified. Please see our
terms of service
for more details
Get an instant quote for your car
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing
What others are asking
How do you use the mechanical key?
If your car has an Intelligent Key system, it also has a mechanical key tucked away inside the body of the remote. This is a vital tool and should be used if the battery dies in your Intelligent Key, as...
broken themostat, broken fan blower
Hey there. These issues may be related or separate problems. If replacing the thermostat provided heat, it was most likely stuck closed and not allowing coolant to flow to the heater core. The blower fan is a completely different circuit....
Water in battery box also flows into electronics and computer
Hello. It is likely that you have an AC drain port that is restricted which will cause water to build up and overflow, or a drain port leaking before the water can properly exit. The AC produces water from the AC compressor and...
Slight engine tick, not a bad sound in one but I'd just like if k could fix it.
There are few situations that require the engine to be revved to 2200 rpm when the transmission is in neutral. Some small ticking noises can come from exhaust leaks at the exhaust manifold (https://www.yourmechanic.com/services/exhaust-manifold-replacement). One thing some people try to...
Can a faulty O2 sensor cause a lean burn?
Hi, thanks for writing in. Yes the O2 sensor can cause the vehicle to run lean. What the O2 sensor does is read the amount of air entering the engine and sends that information to the computer, the computer reads...
the horn honks when turning the key to start the truck?
Both the power to the ignition switch and the ground to the horn relay pass through the clockspring. The clockspring is a spiral-wound electrical connector which allows a vehicle's steering wheel to turn while still making an electrical connection between...
Transmission is skipping 3rd gear
Hello - a "skipping a gear condition (https://www.yourmechanic.com/question/car-skips-gears)" like this is most commonly a failure of the 3-4 gear clutch pack (for the 4L60E transmission). It is also possible that one of the valve passages in the transmission is damaged,...
I replaced new fuel pump and filter and ran good for two days and now it won't start
The fuel pressure should be checked to see if the new fuel pump failed. If pressure is below 40 psi when the key is turned on then replace the fuel pump and filter. When the tank is out you should...
2003 Mercedes-Benz C230 turn signal switch problems
Then turn signal switch internal parts hold it in one direction or the other normally until the steering shaft contacts the lever mechanism and returns it to center. You have a defective turn signal switch and need to replace it....
Related articles
A Buyer’s Guide to the 2012 Nissan Sentra
The The 2012 Nissan Sentra is one of the most versatile sedans in its class. Because it has such a wide variety of options available in its four trims, buyers can choose between a bare-bones version at a very affordable...
2012 Kia Soul vs. 2012 Nissan Cube: Which One Should I Buy?
While technically these two vehicles fall into the “small wagon” classification, they look like nothing more than boxes on wheels. Some people are really into this design, while others are completely opposed to it. If you’re in the former camp,...
The Best Used Cars to Buy If You're a Gardener or Landscape Architect
Gardeners Gardeners and landscape architects need to haul around quite a bit of gear. As a gardener, chances are you will need to transport a variety of mowing equipment, along with smaller implements. You may also need to move shrubs,...
Browse other content
Services
Cities
Maintenance