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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Tools required: OBD-II scanner, multimeter, socket set, torque wrench, oxygen sensor wrench, and safety goggles.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Replace Oxygen Sensors

• Remove the upstream oxygen sensor:

  1. Disconnect the battery to prevent electrical shorts.
  2. Use an oxygen sensor wrench to unscrew the upstream oxygen sensor from the exhaust manifold.
  3. Install the new upstream oxygen sensor and torque it to the manufacturer’s specifications (usually around 30 ft-lbs).

• Remove the downstream oxygen sensor:

  1. Locate the downstream oxygen sensor on the exhaust pipe after the catalytic converter.
  2. Use the oxygen sensor wrench to unscrew the downstream oxygen sensor.
  3. Install the new downstream oxygen sensor and torque it to the manufacturer’s specifications (usually around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter (if necessary)

• Check the catalytic converter:

  1. Inspect for physical signs of damage or clogging.
  2. If the catalytic converter is found to be damaged or clogged, proceed with replacement.

• Remove the catalytic converter:

  1. Unbolt the catalytic converter from the exhaust system using a socket set.
  2. Remove any hangers or brackets holding it in place.

• Install the new catalytic converter:

  1. Position the new catalytic converter in place and secure it with bolts, torquing to specifications.
  2. Reconnect any hangers or brackets.

4. Clear Codes and Test

• Reset the OBD-II system:

  1. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
  2. Reconnect the battery if it was disconnected.

• Test drive the vehicle:

  1. Drive the vehicle for at least 20 minutes to allow the engine to enter closed-loop operation and check for any reoccurring codes.