what does code P0420 mean for my Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the sensor on the exhaust manifold or downpipe.
  2. Use the O2 sensor socket to unscrew it from the exhaust system.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor (if required).
  2. Screw the new sensor into place and tighten to manufacturer specifications (typically around 30 Nm).
• Repeat for the downstream (post-catalytic) oxygen sensor if necessary.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hangers removal tool
• Remove the catalytic converter:
  1. Disconnect any exhaust hangers holding the catalytic converter.
  2. Unbolt the catalytic converter from the exhaust system (use penetrating oil if bolts are rusted).
• Install the new catalytic converter:
  1. Align and bolt the new converter to the exhaust system, torquing bolts to manufacturer specifications (typically around 40 Nm).
  2. Reattach any exhaust hangers removed previously.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the engine control module.