how to fix P0420 code on my Honda Accord 9th Generation (2013-2017)

Solution

1. Preparation

• Gather all tools and parts required for the repair.
• Disconnect the negative battery cable to prevent any electrical shorts.
• Allow the engine to cool before starting work on the exhaust system.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Remove the upstream (pre-catalytic) oxygen sensor using a socket wrench.
• Connect the multimeter to the oxygen sensor wiring to monitor voltage while the engine is running.
• If the voltage fluctuates between 0.1-0.9 volts, the sensor is functioning; replace if constant or outside this range.

3. Check for Exhaust Leaks

• Tools Required: Exhaust leak detector or soapy water
• Use a smoke machine or spray soapy water around joints and connections in the exhaust system.
• Look for bubbles or smoke escaping, indicating a leak; repair any leaks found.

4. Examine the Catalytic Converter

• Tools Required: Socket set, visual inspection tools
• Visually inspect the catalytic converter for any dents, rust, or physical damage.
• Tap gently on the converter; if it rattles, it may be internally damaged and needs replacement.

5. Replace Components as Needed

• Tools Required: Socket set, torque wrench
• If the oxygen sensor is faulty, replace it with a new one, ensuring to torque it to manufacturer specifications.
• If the catalytic converter is damaged, replace it with an OEM or high-quality aftermarket part, following the manufacturer's torque specifications for the bolts.