how to diagnose P0420 code on Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, safety glasses, gloves.
• Disconnect the battery to ensure safety while working on electrical components.

2. Replace Faulty Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from the faulty sensors.
  3. Use a socket wrench to remove the old sensors from the exhaust system.
  4. Install the new oxygen sensors, ensuring they are torqued to the manufacturer's specifications (typically around 30-40 lb-ft).
  5. Reconnect the electrical connectors, ensuring secure fits.

3. Inspect and Replace Catalytic Converter (if needed)

• Sub-steps:
  1. Remove the exhaust heat shields if applicable, using a socket set.
  2. Disconnect the exhaust piping from the catalytic converter using a wrench.
  3. Remove the catalytic converter from its mounting points.
  4. Inspect the old catalytic converter for damage or blockage.
  5. Install the new catalytic converter, ensuring proper torque on all bolts (consult the service manual for torque specifications).
  6. Reattach the exhaust piping and heat shields, if removed.

4. Clear Error Codes

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code and any other stored codes.