how to fix Honda CR-V Fifth Generation (2017-2022) check engine light P0420?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the vehicle to cool down before starting work.

2. Inspect and Test Oxygen Sensors

• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) O2 sensors.
• Using a multimeter, check the voltage output of the upstream O2 sensor; it should fluctuate between 0.1V to 0.9V.
• Check the downstream O2 sensor; it should have a more stable output. If either sensor is outside these parameters, replacement may be necessary.

3. Inspect Catalytic Converter

• Visually check the catalytic converter for any physical damage or signs of overheating (discoloration, dents).
• If suspected to be clogged, perform a backpressure test using a pressure gauge. Normal readings should be below 1 psi at idle.

4. Replace Faulty Components

• If an O2 sensor is faulty, replace it:
  • Use an appropriate O2 sensor socket to remove the old sensor.
  • Apply anti-seize compound to the threads of the new sensor and install it, tightening to manufacturer specifications (usually around 30 ft-lbs).
• If the catalytic converter is faulty:
  • Remove the exhaust pipe or bracket securing it.
  • Unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
  • Install the new catalytic converter, ensuring all gaskets are replaced and torqued to specifications.

5. Reconnect Battery and Clear Codes

• Reconnect the vehicle's battery.
• Use the OBD-II scanner to clear the P0420 code from the system.

6. Test Drive

• Start the vehicle and allow it to reach operating temperature.
• Perform a test drive to ensure the check engine light does not return.