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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, exhaust pipe clamp tool, torque wrench.
• Disconnect the battery negative terminal to ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors.
2. Using a socket set, carefully remove the upstream sensor first.
3. Inspect the sensor for damage or contamination; replace if necessary.
4. Install the new oxygen sensor, ensuring it is torqued to the manufacturer’s specifications (usually around 30 ft-lbs).
5. Repeat for the downstream oxygen sensor.

3. Test and Replace the Catalytic Converter

1. If the oxygen sensors are operational, check the catalytic converter.
2. Measure the inlet and outlet temperatures of the catalytic converter using a temperature probe.
3. If the outlet temperature is not significantly higher (around 100°F or more) than the inlet, the catalytic converter may be faulty.
4. If replacement is necessary, loosen the exhaust clamps and bolts securing the catalytic converter.
5. Remove the old catalytic converter and install the new one, ensuring all bolts are torqued to the specified value (usually around 30-40 ft-lbs).
6. Reconnect any exhaust sensors that were disconnected.

4. Reset the ECM

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