Join Date: Apr 2005
Location: Davie, FL
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Hello everyone. I am a little worried. I brought a used IS300 with 65K miles and week later (around 500 miles after) my CEL and Trac off came on. I went to auto zone, got the error code: P0420. Then I got on here and learned sometimes the sensor gives a bad code, so I reset the car (removed the - from battery) then my CEL +Trac were gone. After 2 weeks (about 700 miles later) my brother put in the wrong gas and the CEL and Trac came back on, so I reset the car again (removed the - for 15min). The CEL and Trac turned off. A week later my CEL and Trac came back on for the third time (I know she is being a bit**). Now I thought I definitely have a problem with my cats. I called up the dealer, he said to bring it in and it might be covered under warranty. The lights have been on for 2 days but tonight on the way home, when I turned the car on, my CEL and tarc light were not on. Drove back home and no lights came on. What the hell is going on? Should I be worried? Has this happened to anyone else? any help will be great. Thanks
That's not exactly an oxygen sensor problem... Or at least it may not be... This is copied/pasted. The codes above are the o2 sensor codes...
P0420 - 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 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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