FAULTBASE
NEWSASKCars
© 2025 FAULTBASE
All rights reserved.
v2.0.0 • Production
ContactPrivacyImpressum
Home/Cars/Honda/Civic/10th Generation (2016-2021)/how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

Honda Civic 10th Generation (2016-2021)

Severity: highDifficulty: mediumError Code: P04202-4 hours
3 min read
539 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix P0420 code related to catalytic converter efficiency in Honda Civic 10th Generation (2016-2021). 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 handling components to prevent burns.

Symptoms

  • •Check engine light illuminated
  • •Decreased fuel efficiency
  • •Poor acceleration
  • •Sulfur smell from exhaust
  • •Failed emissions test

Diagnostic Steps

  1. 1Scan for error codes using an OBD-II scanner to confirm P0420 and check for any additional codes.
  2. 2Inspect the exhaust system visually for any signs of damage or leaks, especially around the catalytic converter.
  3. 3Use a multimeter to test the voltage output of the upstream and downstream oxygen sensors.
  4. 4Check the engine coolant temperature and fuel trim values via the scanner to ensure engine performance is optimal.
  5. 5Inspect the catalytic converter for physical damage or blockage by tapping it gently and listening for rattling sounds.
  6. 6Ensure there are no exhaust leaks upstream of the catalytic converter that could affect sensor readings.

Solution

Solution

1. Preparation

  • Gather necessary tools and parts.
  • Disconnect the battery to prevent electrical shorts.
  • Raise the vehicle securely on jack stands.

2. Inspect and Replace Oxygen Sensors

  • Tools Required: O2 sensor socket, ratchet, torque wrench.
  • Remove the upstream oxygen sensor by using the O2 sensor socket and ratchet.
  • Install the new upstream oxygen sensor by threading it into place and tightening it to the manufacturer’s torque specification (usually around 30 lb-ft).
  • Repeat the process for the downstream oxygen sensor if it is suspected to be faulty.

3. Inspect and Replace the Catalytic Converter

  • Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
  • Remove the bolts securing the catalytic converter to the exhaust system using a socket set.
  • If applicable, cut the exhaust pipe using an exhaust pipe cutter to detach the catalytic converter.
  • Install the new catalytic converter by aligning it with the exhaust system and securing it with bolts, torquing to the manufacturer’s specifications.
  • Ensure all gaskets and seals are replaced to prevent leaks.

4. Reconnect the Battery and Clear Codes

  • Reconnect the battery terminals.
  • Use the OBD-II scanner to clear the P0420 code from the ECM.
  • Start the engine and let it idle to ensure the check engine light does not reappear.

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
  • Socket set
  • Torque wrench
  • Exhaust pipe cutter

Parts Required

  • Upstream oxygen sensor (if faulty)
  • Downstream oxygen sensor (if faulty)
  • Catalytic converter (if damaged)

Additional Information

Error CodeP0420
Component

Exhaust System

Repair Time

2-4 hours

Difficulty

medium

Severity

high

Tools

6 items

Parts

3 items

Related Faults

Discover similar issues

  1. why does my Honda Civic's steering wheel vibrate at high speeds

    Learn how to diagnose and fix steering wheel vibration at high speeds in Honda Civic. Step-by-step guide with diagnostic procedures and repair instruc...

    Component:Suspension
    Symptoms
    • •Steering wheel vibrates noticeably at speeds above 50 mph
    • •Uneven tire wear
    • +{count} more
  2. why is my Honda Civic making a grinding noise when I turn

    Learn how to diagnose and fix grinding noise when turning in Honda Civic. Step-by-step guide with diagnostic procedures and repair instructions.

    Component:Steering
    Symptoms
    • •Grinding noise during turns
    • •Difficulty steering or feeling resistance
    • +{count} more
  3. how to diagnose traction control issues in Honda Civic 9th Generation (2012-2015)

    Learn how to diagnose and fix traction control issues in Honda Civic 2012-2015. Step-by-step guide with symptoms, diagnostic steps, and repair instruc...

    Component:Electrical
    Symptoms
    • •Traction control light illuminated on the dashboard
    • •Loss of traction during acceleration, especially on slippery surfaces
    • +{count} more
  4. why is my Honda Civic using too much oil all of a sudden

    Learn how to diagnose and fix excessive oil consumption in Honda Civic. Step-by-step guide with diagnostic procedures and repair instructions.

    Component:Engine
    Symptoms
    • •Check engine light illuminated
    • •Increased engine noise
    • +{count} more
  5. my Honda Civic won't start but I hear a clicking noise what does this mean

    Learn how to diagnose and fix a Honda Civic that won't start with a clicking noise. Step-by-step guide with diagnostic procedures and repair instructi...

    Component:Electrical
    Symptoms
    • •Clicking noise when turning the ignition key
    • •Engine does not crank
    • +{count} more
  6. why does my Honda Civic make a popping noise when turning

    Learn how to diagnose and fix popping noise when turning in Honda Civic. Step-by-step guide with diagnostic procedures and repair instructions.

    Component:Suspension
    Symptoms
    • •Popping or clicking noise during left or right turns
    • •Noise increases with sharp turns or while maneuvering at low speeds
    • +{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