how to fix Honda Civic 11th Generation (2022-Present) P0420 code

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, exhaust gas temperature (EGT) gauge.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Step 1: Locate the upstream and downstream oxygen sensors.
• Step 2: Use a socket to carefully remove the sensors from the exhaust piping.
• Step 3: Inspect the sensors for damage or contamination; replace with new sensors if necessary.
• Step 4: Install the new oxygen sensors and torque them to the manufacturer's specifications (typically around 30 ft-lbs).
• Step 5: Reconnect the electrical connectors for both sensors.

3. Inspect and Replace the Catalytic Converter

• Step 1: If the oxygen sensors are functioning properly, inspect the catalytic converter for physical damage or signs of clogging.
• Step 2: If replacement is necessary, loosen any clamps or bolts securing the catalytic converter to the exhaust system.
• Step 3: Remove the old catalytic converter and install the new one, ensuring proper alignment.
• Step 4: Tighten all connections to the specified torque values.
• Step 5: Reconnect any exhaust hangers that were removed.

4. Reconnect Battery and Clear Codes

• Step 1: Reconnect the negative battery terminal.
• Step 2: Use the OBD-II scanner to clear the P0420 code from the vehicle's ECU.
• Step 3: Start the engine and allow it to reach operating temperature.