how to fix P0420 code on Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical shocks.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the upstream oxygen sensor using a socket wrench.
   • Tools Required: Oxygen sensor socket, wrench set.
   • Safety Warning: Wear gloves and safety goggles.
3. Install the new upstream oxygen sensor and torque it to the manufacturer's specifications (usually around 30 ft-lbs).
4. Repeat the process for the downstream oxygen sensor if the readings were abnormal.

3. Inspect and Clean Catalytic Converter

1. Remove the catalytic converter from the exhaust system.
   • Tools Required: Socket set, exhaust hanger removal tool.
2. Inspect the catalytic converter for any signs of physical damage or excessive carbon buildup.
3. If the converter is clogged, clean it using a specialized catalytic converter cleaner, following the product's instructions.
4. If damage is found, replace the catalytic converter with a new OEM or high-quality aftermarket unit.
   • Parts Required: New catalytic converter, if necessary.

4. Reassemble and Test

1. Reinstall the catalytic converter and tighten all bolts to the specified torque (usually around 40-50 ft-lbs).
2. Reconnect the oxygen sensors and battery.
3. Start the engine and allow it to reach operating temperature while checking for leaks in the exhaust system.