Q: I have a po420 code and suspect my flex pipe between the two cats is leaking. Could that be a possibility of why that code is comi

asked by on

I'm getting a po420 code. I am experiencing slow acceleration. My exhaust setup is cat attached to manifold into flex pipe into a second cat with the only 02 sensors before and after the first cat. Is it possible the code could be from a small leak in the flex pipe? If not what are the chances it's the second cat even though there's no sensors after it??

The downstream oxygen sensor (post converter) monitors the efficiency of the catalytic converter. If there is no downstream sensor after the second converter then the P0420 code cannot arise from a fault there. Exhaust leaks have to repaired anyway, due to the risks of carbon monoxide poisoning, so the best thing to do is repair the leak. Although in certain circumstances leaks can cause P0420 to set I wouldn’t count on a resolution but, as noted, the leak has to be repaired anyway so that is a good place to start. Generally, P0420 sets due to catalyst efficiency being out of range but there are many engine operating problems that can cause out of range catalyst operation. In other words, P0420 does not necessarily mean the catalyst itself is performing poorly; it could be an engine issue. Although, in your circumstance, with slow acceleration, and a P0420 code, a partially blocked converter would be considered in the diagnostic. The bottom line is, to resolve your issue the recommended service is a slow acceleration diagnostic. If you request that service, the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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. I have a po420 code and suspect my flex pipe between the two cats is leaking. Could that be a possibility of why that code is comi

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: Hello, I was curious to know how much would a transmission fluid change cost for a 2013 Scion XB? What type of fluid do they use?

Hi there. The transmission fluid that your vehicle calls for is Genuine Toyota ATF T-IV Transmission Fluid. If you have letters to have your vehicle brought to the dealership for a recall, there is no charge to you to fix...

Q: 2012 Chevy traverse rear cabin hvac fan continues to run when the vehicle is turned off. How can I fix this?

If there is a relay in the circuit, it is possible the relay contacts are stuck closed. The switch could be stuck, too. Inasmuch as micro- and PC-board mounted relays are used, really the thing to do is use the...

Q: Fluid leaking - 2009 Chevrolet Malibu

There should not be ANY leaks or seepage. One obvious thing to check is the drain plug/gasket (if equipped). It is also possible that fluid is leaking past the transmission oil pan gasket if the pan was removed and a...

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 Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
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...