how to fix Honda CR-V Fifth Generation (2017-2022) error code P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery.
• Allow the vehicle to cool completely before starting work.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor using a wrench.
• Connect the multimeter to the sensor's terminals and start the engine. Voltage should fluctuate between 0.1V to 0.9V.
• If out of range, replace the oxygen sensor.

3. Inspect and Test Catalytic Converter

• Tools Required: Backpressure gauge.
• Remove the downstream (post-catalytic) oxygen sensor.
• Insert the backpressure gauge into the exhaust pipe.
• Start the engine and observe the gauge. A reading above 3 psi indicates a clogged catalytic converter.
• If clogged, replace the catalytic converter.

4. Replace Components

• If either the oxygen sensor or catalytic converter is faulty, proceed with replacement:
  • For Oxygen Sensor:
    • Install the new oxygen sensor and torque to manufacturer's specifications (usually around 30-40 lb-ft).
  • For Catalytic Converter:
    • Remove any mounting bolts and hangers.
    • Install the new catalytic converter, ensuring proper alignment and sealing.
    • Torque bolts to specifications (typically 25-35 lb-ft depending on the model).

5. Reconnect and Reset

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the error codes.
• Start the engine and allow it to idle for a few minutes to check for any error codes reappearing.