Question about Ford Cars & Trucks
I have p0420 code on my Ford 250 Super Duty.It says that the catalytic converter is bad. I want to make sure that it is correct testing the O2 sensors before replacing the cat
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Posted on Jan 02, 2017
from what i am finding the code means o2 sensors. they recommend replacing them and if this does not work than replacing the cat converter
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
A code P0420 may mean that one or more of the following has happened:
Some suggested steps for troubleshooting a P0420 code include:
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Posted on Aug 20, 2009
SOURCE: P0420 and P0430
The AF sensors are uupstream and the O2 down stream. The car' s computer tests them and it is saying your cats are bad. If you have a scan tool you could look at the data and see what the sensors are seeing. The Af sensors are the ones that control the fuel ratio in the car while the O2's just watch. AF's would be the one to change but there is no garuatee that the codes won't come back.
Posted on Sep 25, 2009
This started out as being a one code issue. I have no idea as to what you have done so far beyond what I have recommended. If you didn't take the intake off then there is no reason to believe the gasket is bad.
Posted on Jan 20, 2010
I do not know for sure if this is the problem you are having, But, I have noticed that from 95 up to 2002 I have seen a lot of PO420 codes that have been just the sensor. I do not know if it was a weak sensor or just that program telling it that it is below threshold. I did notice that if the vehicles are run for a long trip at highway speed it goes out. I wish you luck and have a great day.
Posted on Feb 11, 2010
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