Question about 2002 Chevrolet Blazer
The code p0420 as you probably know is a Cat efficiency code. You did the right thing replacing the o2 sensors first. The code sets when the rear o2 sensors switching rate gets within a certain range of the front o2 sensors switching rate. A lazy slow switching sensor could set a false p0420 code. However, since you know you have good o2 sensors installed the catalytic converter is going to need to be replaced to get rid of the code. I suggest only using OEM converters. Nearly every aftermarket converter i've installed came back 6 months later with the same code. When we use OEM converters the code is gone for good.
If you end up spending the money on a new converter make sure your engine is running well and you have no missfire codes as that's a large cause of cat failures.
Posted on Jun 04, 2010
Code P0420 is a code for Catalyst efficiency. The computer is seeing the post Catalytic converter o2 sensor having too much activity. The Cat. should be cleaning the exaust of Hc, co, and Nox. The post cat o2 will read the o2 content in the exhaust and if it moves up and down too much or to high and low, the computer interperates that as the cat not ridding the exhaust of it's pollutants. This indicates that the converter is unable to preform properly. The problem could be a bad cat, o2 sensor (Pre- and/or post cat)or o2 sensor wires, or an air fuel mixture problem that has caused the cat to fail. Many other engine operating system failures can cause the converter to not work properly.
Posted on Jun 01, 2010
P0420 is not necessarily the O2 sensor. The most common reason for this code is the cat converter itself. The tail pipe sensor is only rarely causing this DTC.
Observing the cat at a glance is not enough to find the fault. You will need to perform an emission test on the exahust system. You will probably find that emission are high because the cat converter must be replaced.
Do an emission test and eventually replace cat converter or full exhaust system, depending on conditions.
Posted on Jun 01, 2010
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Posted on Jan 02, 2017
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