FAULTBASE
NEWSASKCars
© 2025 FAULTBASE
All rights reserved.
v2.0.0 • Production
ContactPrivacyImpressum
Home/Cars/Honda/Civic/9th Generation (2012-2015)/how to fix Honda Civic 9th Generation (2012-2015) P0420 error code

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

Honda Civic 9th Generation (2012-2015)

Severity: mediumDifficulty: mediumError Code: P04202-4 hours
3 min read
544 words

Problem Statement

Learn how to diagnose and fix P0420 error code related to catalytic converter efficiency in Honda Civic 9th Generation. Step-by-step guide included.

Error Code
P0420
Component
Exhaust System
Repair Time
2-4 hours

Safety Warnings

  • ⚠Disconnect the battery before working on electrical systems.
  • ⚠Allow the exhaust system to cool before touching any components.

Symptoms

  • •Check engine light illuminated
  • •Decreased fuel economy
  • •Poor acceleration
  • •Emissions test failure
  • •Unusual exhaust smells (rotten egg odor)

Diagnostic Steps

  1. 1Scan for error codes using an OBD-II scanner to confirm P0420 and any related codes.
  2. 2Inspect the exhaust system for visible damage or leaks, particularly around the catalytic converter.
  3. 3Check the oxygen sensor readings before and after the catalytic converter using a multimeter or scan tool.
  4. 4Inspect for exhaust leaks upstream of the catalytic converter.
  5. 5Measure the temperature of the catalytic converter inlet and outlet using an infrared thermometer to assess its efficiency.
  6. 6Verify that the fuel trim values are within the manufacturer’s specifications.

Solution

Solution

1. Preparation

  • Gather all necessary tools and parts.
  • Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

  1. Locate Oxygen Sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Unplug the Sensors: Carefully disconnect the electrical connectors from both sensors.
  3. Remove the Sensors: Use an oxygen sensor socket to unscrew and remove the sensors.
  4. Install New Sensors: Apply anti-seize compound on the threads of the new oxygen sensors and install them in the same locations.
  5. Reconnect Electrical Connectors: Securely connect the electrical connectors to the new sensors.

3. Inspect and Replace the Catalytic Converter

  1. Remove Exhaust Components: If necessary, remove any exhaust heat shields or brackets to gain access to the catalytic converter.
  2. Unbolt the Catalytic Converter: Use a socket set to remove the bolts securing the catalytic converter to the exhaust manifold and exhaust pipe.
  3. Inspect Gasket: Check the exhaust gaskets for wear; replace if necessary.
  4. Install New Catalytic Converter: Position the new catalytic converter and secure it with bolts. Tighten to manufacturer’s specifications (typically around 24-30 lb-ft).
  5. Reinstall Exhaust Components: Replace any heat shields or brackets that were removed.

4. Reconnect Battery and Clear Codes

  1. Reconnect the Battery: Reattach the negative battery terminal and ensure a secure connection.
  2. Clear Codes: Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.

Verification

After completing the repair, verify that the issue has been resolved:

  • Test the affected component to ensure it functions correctly
  • Check for any error codes or warning lights
  • Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

  • •Follow the manufacturer's recommended maintenance schedule
  • •Address warning signs early before they develop into major issues
  • •Use quality parts and fluids recommended for your vehicle
  • •Keep detailed records of all repairs and maintenance

Tools & Equipment Required

  • OBD-II scanner
  • Oxygen sensor socket
  • Socket set
  • Torque wrench
  • Infrared thermometer

Parts Required

  • New upstream oxygen sensor
  • New downstream oxygen sensor
  • New catalytic converter (if necessary)
  • Gaskets (if worn)

Additional Information

Error CodeP0420
Component

Exhaust System

Repair Time

2-4 hours

Difficulty

medium

Severity

medium

Tools

5 items

Parts

4 items

Related Faults

Discover similar issues

  1. how to fix a Honda Civic 9th Generation (2012-2015) transmission slipping issue

    Learn how to diagnose and fix transmission slipping issues in Honda Civic 9th Generation (2012-2015). Step-by-step guide with tools and parts required...

    Component:Transmission
    Symptoms
    • •Check engine light illuminated
    • •Engine RPM increases without corresponding acceleration
    • +{count} more
  2. why does my Honda Civic 9th Generation (2012-2015) heater smell like antifreeze?

    Learn how to diagnose and fix the heater smell like antifreeze in Honda Civic 9th Generation (2012-2015). Step-by-step guide with diagnostic procedure...

    Component:HVAC
    Symptoms
    • •Sweet odor resembling antifreeze inside the cabin
    • •Windows fogging up more than usual
    • +{count} more
  3. why does my Honda Civic 9th Generation (2012-2015) transmission slip when accelerating

    Learn how to diagnose and fix transmission slipping issues in Honda Civic 9th Generation (2012-2015). Step-by-step guide with diagnostic procedures an...

    Component:Transmission
    Symptoms
    • •Transmission slips during acceleration
    • •High RPMs without corresponding increase in speed
    • +{count} more
  4. how to find a steering fluid leak in my Honda Civic 9th Generation (2012-2015)

    Learn how to find and fix a steering fluid leak in your Honda Civic 9th Generation (2012-2015). Step-by-step guide with diagnostic procedures and repa...

    Component:Steering
    Symptoms
    • •Check engine light may illuminate due to low fluid levels
    • •Difficulty steering or increased steering effort
    • +{count} more
  5. what are the symptoms of a bad wheel bearing on Honda Civic 9th Generation (2012-2015)

    Discover the symptoms of a bad wheel bearing on Honda Civic 9th Generation (2012-2015) and learn how to diagnose and fix the issue with our step-by-st...

    Component:Suspension
    Symptoms
    • •Grinding or humming noise that increases with vehicle speed
    • •Vibration in the steering wheel or through the vehicle
    • +{count} more
  6. why does my Honda Civic 9th Generation (2012-2015) vibrate at high speeds?

    Learn to diagnose and fix high-speed vibrations in Honda Civic 9th Generation. Step-by-step guide with symptoms, diagnostic steps, and repair instruct...

    Component:Suspension
    Symptoms
    • •Vibration felt through the steering wheel
    • •Vibration through the floorboard or seat
    • +{count} more

Share this solution

Comments

Sign in to share your thoughts

Sign In

No comments yet

Be the first to share your thoughts

Back to Generation