Q: Q: P0420 code

asked by on

I'm having the P0420 code on my SUV. I had just filled the tank when it came on, so I tightened the cap. The code cleared for about 1/4 the tank and then came back on and stayed the rest of that tank. The same thing happened again when I filled the tank to Full. What causes this problem?

Honda has a technical service bulletin (TSB) out for this condition. There are 2 possibilities to correct this fault, according to the bulletin:

  1. Replace the catalytic converter
  2. Software update of the engine computer

One last thing to consider is the post catalytic oxygen sensor. To avoid a trip to the dealer, you may want to enlist the help of a mechanic to check the post catalytic oxygen sensor and inspect the exhaust system for leaks.

If the engine computer software has not ever been updated, then you will have to go to the dealer to correct this.

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. Q: P0420 code

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: What does the 15% next to my oil light mean?

Hi, thanks for writing in. I'd be happy to help. This is telling you that your car has 15% life on the oil left, before it is recommended to change it. Make sure the person that changes the oil and...

Q: car stall occasionally

Common causes of engine stalling and rough idle include a faulty mass airflow sensor, faulty engine coolant temperature switch/sensor (typically at cold start only), worn spark plugs, wires or defective ignition coil(s), inadequate fuel delivery or pressure (clogged fuel filter,...

Q: when i turn my steering wheel to the right--even slightly--my engine stops. why

Hi there, thanks for writing in. I have never experienced this exact issue before. First we should address the vacuum leak, which could cause the car to stall while idling, as well as being a potential cause of the oxygen...

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...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
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...