Q: Catalyst system efficiency

asked by on

I am getting code P0420, catalyst system efficiency below threshold.

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.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Catalyst system efficiency

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

Get a quote

What others are asking

Q: Both headlights went out (not at the same time) for 2013 Cadillac ATS. Checked fuses looked ok. Could both halogens go out at arou

If the bulbs are both the same age, it would not be exceptional for them to fail at around the same time. A standard halogen headlight bulb could operate as long as 1,000 hours or so. A long life bulb...

Q: Can a Catalytic converter break up little pieces and ruin your engine

It is not possible for broken off pieces from a catalytic converter to get into your car's engine and damage it. However, if your vehicle's catalytic converter is damaged, including breakage or melting of the internal honeycomb substrate that contains...

Q: Q: Having problems starting the car.

Hello, it takes 3 things to make a car run, air, spark and fuel. It sounds like it is taking a while to get fuel or its losing fuel pressure. This could be a sign that the fuel pump is...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.