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

how to troubleshoot a P0420 code on my Honda Civic 9th Generation (2012-2015)

Honda Civic 9th Generation (2012-2015)

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

Problem Statement

Learn how to troubleshoot and fix P0420 code in Honda Civic 9th Generation. Step-by-step guide with diagnostic steps and repair instructions.

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

Safety Warnings

  • ⚠Disconnect the battery before working on electrical systems.
  • ⚠Allow the engine to cool before opening the exhaust system.

Symptoms

  • •Check engine light illuminated
  • •Decreased fuel economy
  • •Poor engine performance or rough idle
  • •Failed emissions test
  • •Unusual exhaust smell (rotten egg odor)

Diagnostic Steps

  1. 1Scan the vehicle's OBD-II system to confirm the P0420 code and check for any additional trouble codes.
  2. 2Inspect the exhaust system for visible leaks or damage, focusing on the area before and after the catalytic converter.
  3. 3Measure the voltage output of the upstream and downstream oxygen sensors using a multimeter to compare readings.
  4. 4Check for exhaust backpressure using a pressure gauge to ensure proper flow through the exhaust system.
  5. 5Inspect the catalytic converter visually for any signs of external damage or signs of overheating.
  6. 6Verify the fuel trim readings to ensure that the engine is running within specifications.

Solution

Solution

1. Preparation

  • Gather all necessary tools and parts.
  • Disconnect the negative battery terminal to prevent electrical shorts.
  • Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

  • Tools Required: O2 sensor socket, ratchet, torque wrench, multimeter.
  • Steps:
    1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
    2. Use the O2 sensor socket to carefully remove the upstream oxygen sensor from the exhaust manifold.
    3. Inspect the sensor for damage; replace it if necessary.
    4. Repeat the process for the downstream oxygen sensor.
    5. Install the new sensors, ensuring they are torqued to the manufacturer’s specifications (typically around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter

  • Tools Required: Socket set, jack and jack stands, exhaust pipe cutter, gasket scraper.
  • Steps:
    1. Lift the vehicle using a jack and secure it on jack stands.
    2. Remove the bolts securing the catalytic converter to the exhaust system using a socket set.
    3. Use an exhaust pipe cutter if necessary to remove the catalytic converter.
    4. Clean the mating surfaces on the exhaust pipes to remove any debris or old gasket material.
    5. Install the new catalytic converter and secure it with new bolts, ensuring they are torqued to manufacturer specifications.
    6. Reconnect any heat shields or brackets that were removed.

4. Reset the ECU

  • Reconnect the negative battery terminal.
  • Start the engine and allow it to reach operating temperature.
  • Use an OBD-II scanner to clear the P0420 code from the system.

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
  • Multimeter
  • O2 sensor socket
  • Ratchet
  • Torque wrench
  • Exhaust pipe cutter
  • Socket set
  • Jack and jack stands

Parts Required

  • Upstream oxygen sensor
  • Downstream oxygen sensor
  • Catalytic converter

Additional Information

Error CodeP0420
Component

Exhaust System

Repair Time

2-4 hours

Difficulty

medium

Severity

medium

Tools

8 items

Parts

3 items

Related Faults

Discover similar issues

  1. my Honda Civic 9th Generation (2012-2015) won't start and just clicks

    Learn how to diagnose and fix the no-start clicking issue in Honda Civic 9th Generation (2012-2015). Step-by-step guide with diagnostic procedures and...

    Component:Electrical
    Symptoms
    • •Engine does not crank
    • •Single or multiple clicking noise from the starter area
    • +{count} more
  2. why is my Honda Civic 9th Generation (2012-2015) making a weird noise when turning

    Learn how to diagnose and fix steering noise in Honda Civic 9th Generation (2012-2015). Step-by-step guide with symptoms, diagnostic steps, and repair...

    Component:Steering
    Symptoms
    • •Grinding or squeaking noise when turning the steering wheel
    • •Clunking sound during sharp turns
    • +{count} more
  3. my Honda Civic 9th Generation (2012-2015) pulls to one side when driving, why is that?

    Learn how to diagnose and fix pulling issues in Honda Civic 9th Generation. Step-by-step guide with symptoms, diagnostic steps, and repair instruction...

    Component:Suspension
    Symptoms
    • •Vehicle pulls to the left or right while driving straight
    • •Uneven tire wear on front tires
    • +{count} more
  4. how to fix a Honda Civic 9th Generation (2012-2015) that won’t start at all

    Learn how to diagnose and fix starting issues in Honda Civic 9th Generation (2012-2015). Step-by-step guide with symptoms, diagnostic steps, and repai...

    Component:Electrical
    Symptoms
    • •No engine crank or turnover
    • •Dashboard lights illuminating but no response when turning the key
    • +{count} more
  5. how to replace the cabin air filter in my Honda Civic 9th Generation (2012-2015)?

    Step-by-step guide on how to replace the cabin air filter in your 2012-2015 Honda Civic. Improve airflow and eliminate odors with this easy fix.

    Component:HVAC
    Symptoms
    • •Reduced airflow from the HVAC system
    • •Unpleasant odors from the vents
    • +{count} more
  6. why does my Honda Civic 9th Generation (2012-2015) smell like gas

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

    Component:Fuel System
    Symptoms
    • •Strong gasoline smell in or around the vehicle
    • •Fuel leaks visible under the vehicle
    • +{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