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.
causes
A code P0420 may mean that one or more of the following has happened:
- Leaded fuel was used where unleaded was called for
- An oxygen sensor is not reading (functioning) properly
- The engine coolant temperature sensor is not working properly
- Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
- Retarded spark timing
- The oxygen sensors in front and behind the converter are reporting too similar
of readings
possible soloutions
Some suggested steps for troubleshooting a P0420 code include:
- Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair
as required.
- Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor
in front of the catalytic converter normally has a fluctuating waveform. The
waveform of the sensor behind the converter should be more steady).
- Inspect the downstream heated oxygen sensor (HO2), replace if necessary
- Replace the catalytic converter
One thing to note is that many
vehicle manufacturers offer a longer warranty
on emissions-related parts. So if you have a newer car but it's out of it's
bumper-to-bumper warranty, there still may be warranty on this type of problem.
Many manufacturers give a five year, unlimited
mileage warranty on these items.
It's worth checking into.
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