Question about 2000 Hyundai Elantra
Catalyst System Efficiency Below Threshold (Bank 1)
What does that mean?
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.
You will likely not notice any drivability problems, although there may be symptoms.
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
Some suggested steps for troubleshooting a P0420 error 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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Posted on Sep 07, 2010
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Posted on Jan 02, 2017
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Sep 04, 2016 | 2004 Cadillac Deville
Catalyst System Bank 1 Low Efficiency
Air leaks at the exhaust manifold or in the exhaust pipesBase engine problems (i.e., high engine oil or coolant usage).Catalytic converter is damaged, contaminated or has failed.Continuous engine misfire conditions, or weak or low coil output.Front HO2S or rear HO2S is contaminated with fuel or moisture.Rear HO2S is loose in the mounting hole (check it for a leak).Front HO2S older (aged) than the rear HO2S (HO2S-12 is lazy).Click here to see.
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