I have code poo11 and po420 what do I check

Greg Bernett

• 2993 Answers
• Posted on Mar 29, 2009

SOURCE: 1997 toyota camry check engine light on,code po440,po420,po441,

P0420 is catalyst system efficiency below threshold (bank 1)

P0440 is evaporative emission control system malfunction

P0441 is evaporative emission control system incorrect purge flow

SOURCE: PO420

Not just a faulty catalytic converter will trigger this code. Many other issues can trigger this code.

• 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
• Delayed spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

• Check for exhaust leaks at the manifold, pipes, catalytic converter.
• Replace Coolant Temperature Sensor
  
• 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 the catalytic converter
• Have timing adjusted
  

SOURCE: 2000 corolla with trouble code po420

If the code has cleared on its own then you need to disconnect the battery and re-connect it. This will clear the codes out of the memory. If you don't want to do this you can go to an auto parts strore and have them hook the little computer up to your car and they can clear out the code as well.

SOURCE: my 01 toyota sienna has check engine light on code

If you think the catylist is ok check your 02 sensor instead. P0420 is about the convertor and maybe water got in your tank fron filling it at a fuel stop with low reserves in their tank. They all do have water in their tanks. If you like fill your tank and the disconnect your battery for 15 minutes. reconnect it and drive the car 50 miles or more on the highway. This may clear your codes out

SOURCE: po420 on my 2001 sienna

P0420=Catalyst System Efficiency Below Threshold Bank 1,
The air filter is not the cause here,this is just a code saying your converter is not doing its best,