Honda Civic 9th Generation (2012-2015) check engine light on with code P0420 what does it mean

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Allow the vehicle to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench

• Remove the upstream (pre-catalytic) oxygen sensor:

  1. Locate the sensor on the exhaust manifold.
  2. Use an O2 sensor socket to unscrew the sensor from the exhaust pipe.
  3. Install the new oxygen sensor and tighten it to manufacturer specifications (usually between 30-40 ft-lb).

• Remove the downstream (post-catalytic) oxygen sensor:

  1. Locate the sensor after the catalytic converter.
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust pipe.
  3. Install the new oxygen sensor and tighten it to manufacturer specifications.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Wrench set, socket set, torch (if rusted), exhaust hanger removal tool
• If the oxygen sensors are functioning correctly but the code persists:
  1. Inspect the catalytic converter for damage or clogging.
  2. Remove the catalytic converter by loosening the bolts that secure it to the exhaust system.
  3. Replace with a new catalytic converter, ensuring that gaskets are in good condition.
  4. Reattach the exhaust system and tighten all bolts to manufacturer specifications.

4. Clear Check Engine Light

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code from the ECU.