P0430 OBD-II Trouble Code: Catalyst System Efficiency Below Threshold (Bank 2)

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Cost of diagnosing the P0430 code

P0430 is a diagnostic trouble code (DTC) for "Catalyst System Efficiency Below Threshold (Bank 2)". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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P0420 code definition

P0420 is a generic diagnostic trouble code that indicates a malfunction within the catalyst system. It may been seen with misfire codes and oxygen sensor codes.

What the P0420 code means

The P0420 code is set when the ECU detects below threshold performance from the catalytic converter. The ECU monitors the catalytic converter closely and when a the low performance threshold is detected the Check Engine Light will be displayed on the dashboard.

What causes the P0420 code?

  • Faulty catalytic converter
  • Engine misfire
  • Fuel injector leaking
  • Engine mechanical damage
  • Oxygen sensor that has improper readings
  • Exhaust leak

What are the symptoms of the P0420 code?

  • The presence of the Check Engine Light displaying on the dashboard.

  • The vehicle may have a dipping idle and a slight lack of power.

  • Catalytic codes may make the Check Engine Light flash on the dashboard.

How does a mechanic diagnose the P0420 code?

  • Installs the scan tool to the vehicle's DLC port and check for any codes present

  • Notes freeze frame data for every code found, this indicates the vehicle's conditions at the time the code was set

  • Clears all of the codes present

  • Performs a road test under similar conditions to the freeze frame data to confirm the problem

  • Performs a visual inspection of the exhaust system

  • Checks for any exhaust leaks

  • Uses a scan tool to monitor the oxygen sensor data and checks for proper operation

Common mistakes when diagnosing the P0420 code

Mistakes can be made easily when a mechanical problem is overlooked as the cause for the P04020 code such as a leaking fuel injector or a leaking head gasket. In some vehicles the oxygen sensor may have improper readings causing the catalytic converter code to be found.

How serious is the P0420 code?

P0420 can be a serious repair if the catalytic converter has failed. These parts are often expensive as they contain rare earth metals. Once the P0420 code is found the vehicle should be repaired ASAP to avoid damage to the catalytic converter.

What repairs can fix the P0420 code?

  • Replacing the catalytic converter
  • Diagnosing and repairing the engine misfire
  • Replacing the fuel injector
  • Repairing any mechanical damages in the engine
  • Replacing the oxygen sensor
  • Repairing or replacing the exhaust replaced

Additional comments for consideration regarding the P0420 code

Without the proper tools the P0420 can be difficult or downright impossible to diagnose properly. Many different systems and components can cause the P0420 code. Once tool needed is an advanced level scan tool, this allows technicians to view misfires, oxygen sensor readings, and live data. All of this aids in accurate diagnosis and avoids costly repairs that are not needed.

Need help with a P0100 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6220.

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