Catalytic converter or Oxygen sensor

Common causes of the P0420 code

• Damaged muffler or leaks in the muffler.
• Damaged exhaust manifold or leaks in the exhaust manifold.
• Damaged exhaust pipe or exhaust pipe leaks.
• A misfire in the engine.
• Oil contamination in catalytic converter.
• Faulty catalytic converter (most common).
• Faulty engine coolant temperature sensor.
• Faulty front oxygen sensor.
• Faulty rear oxygen sensor.
• Damaged oxygen sensor wiring.
• Oxygen sensor wiring that is not properly connected.
• Damaged oxygen sensor connectors
• A leaking fuel injector.
• High fuel pressure.
• Use of the wrong kind of fuel (using leaded fuel instead of unleaded fuel)

code p 430 refers to catalytic converter system , bank 2---efficiency below threshold ====causes ---cat converter--wiring ---Heated oxygen sensor (HO2S in the exhaust manifold bank 2 before the cat converter)
have the cat converter checked for failure and blocking the exhaust

Check the relays and fuses for the H.E.G.O (heated oxygen sensors) for power and function.

DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
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
******** 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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Catalyst System Efficiency Below Threshold (Bank 1)

A code PO420 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 reading

• 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

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

Possible solutions:

• 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
  

if u have one oxygen sensor then u need to take a deep look at the bottom of ur car it will be somewhere at the Exhaust pipe if u have a catalytic converter then u will have two oxygen sensors one before the catalytic converter & the other will be after the catalytic converter. Note: the catalytic converter is located at after a little bit of beginning in Exhaust pipe.

a bad or disconnected oxygen sensor will make the engine run rich.
How about a clogged air filter? 

Some cars have 2 sensors. The oxygen sensor and the outlet sensor. One checks the O2 level when it goes in , the other checks the output levels on the outtake . Usually located on the outake manifold or the pipe itself under the car. past the catalytic converter.

Catalyst System Efficiency Below Threshold (Bank 1)

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.

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


To Do list

* 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