DTC code P0420

  • 2007 FORD FOCUS
  • 4 CYL
  • 2WD
  • 30,000 MILES
Catalyst efficiency low-bank 1
checked for vacuum leaks found none
engine has stable idle and no misfire detected
checked and cleaned egr valve and tube
checked catalytic converters but ok
newly installed fuel pump
30,000 kms odometer
noticed that check engine appears with dtc code p0420 on a long distance driving but before it appears the engine quits. After engine quits then restarted the engine, engine runs back to normal
Do you
have the same problem?
Tuesday, March 29th, 2011 AT 3:04 PM

1 Reply

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 Solutions 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
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Tuesday, March 29th, 2011 AT 6:41 PM

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