how to fix the P0420 code on my Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to avoid electrical shorts during the repair process.

Tools Required:

• OBD-II scanner
• Multimeter
• Socket set
• Torque wrench
• Ratchet and extensions

2. Inspect and Replace O2 Sensors

• Sub-step 1: If O2 sensors are found faulty, remove the upstream (pre-catalytic) O2 sensor by using a socket wrench. Be cautious as the sensor may be hot if the engine was recently running.
• Sub-step 2: Install the new O2 sensor, ensuring it is tightened to the manufacturer's specifications (usually around 30 ft-lbs).
• Sub-step 3: Repeat the process for the downstream (post-catalytic) O2 sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Sub-step 1: If the catalytic converter is damaged or clogged, remove it from the exhaust system. This often involves unbolting it from the exhaust pipe and the exhaust manifold.
• Sub-step 2: Install the new catalytic converter, ensuring that the gasket is in place and that all bolts are torqued to specifications (usually around 25-30 ft-lbs).
• Sub-step 3: Reconnect exhaust hangers and ensure there are no leaks at the joints.

4. Reset the Engine Control Module (ECM)

• Sub-step 1: Reconnect the battery.
• Sub-step 2: Use the OBD-II scanner to clear the P0420 code from the ECM.
• Sub-step 3: Start the engine and allow it to reach operating temperature to check for any reoccurrence of the code.