P0420 Error Code

[KMR]

I purchased my ES330 with 50,000 miles. Not long after the VSC / Trac Off / Check Engine lights came on. About a week later they went off on their own. This repeated itself in approximately one year intervals, usually during cold weather. Recently the lights came on and stayed on. The Toyota dealer read the P0420 code and recommended that the A/F Ration Sensor on Bank 1 be replaced. They mentioned that if this did not fix the problem, then the catalytic converter would have to be replaced. Replacing the A/F sensor did not fix the problem. I would expect that if the cat converter were bad, it would not be an intermittent problem.

I have seen this topic come up many times, but not for an 2005 ES330. This is why I am starting a new topic. Based on what I have seen on LOC, the problem is right up there with the "transmission hesitation" problem. Also I have noticed that the problem seems to be more prevalent on Bank 1?

Is there any update information on this topic?

[atl530i]

I had this same error in my Altima, I ended up replacing the cat converter and both of the O2 sensors since they were cheap anyway.

[paulenka1]

A code P0420 may mean that one or more of the following has happened:

• Leaded fuel was used where unleaded was called for
  
• A damaged or failed oxygen sensor (HO2S)
  
• Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
  
• The engine coolant temperature sensor is not working properly
  
• Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
  
• Retarded spark timing
  
• The oxygen sensors in front and behind the converter are reporting too similar of readings
  
• Leaking fuel injector or high fuel pressure
  
• Cylinder misfire
  
• Oil contamination
  

you can get a code scanner to clear the fault code.

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chinasinoy

[hdygma]

I dont know if you still have this issue but I had an 0402 code with Traction Control light and solved it as follows...

http://us.lexusownersclub.com/forums/topic/33746-dtc-p0402/