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Home/Cars/Honda/Civic/10th Generation (2016-2021)/how to fix P0420 code in Honda Civic 10th Generation (2016-2021)

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

Honda Civic 10th Generation (2016-2021)

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

Problem Statement

Learn how to diagnose and fix P0420 exhaust system issue in Honda Civic 10th Generation. Step-by-step guide with diagnostic procedures 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 exhaust system to cool before inspection or repairs.

Symptoms

  • •Check engine light illuminated
  • •Decreased fuel economy
  • •Engine misfire or rough idle
  • •Failed emissions test
  • •Unusual exhaust odors (e.g., sulfur smell)

Diagnostic Steps

  1. 1Scan the vehicle’s OBD-II system for error codes and document all related codes.
  2. 2Inspect the exhaust system for any visible leaks or damage, particularly near the catalytic converter.
  3. 3Check the oxygen sensors (pre and post-catalytic converter) for proper operation and connection.
  4. 4Measure the voltage output of the upstream and downstream oxygen sensors using a multimeter.
  5. 5Perform a visual inspection of the catalytic converter for any signs of physical damage or blockage.
  6. 6Test drive the vehicle under various conditions to see if the code reappears.

Solution

Solution

1. Preparation

  • Gather tools and parts required.
  • Disconnect the negative battery terminal to prevent electrical shock.

2. Inspect and Replace Oxygen Sensors

  • Tools Required: O2 sensor socket, ratchet, torque wrench.
  • Steps:
    1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
    2. Disconnect the electrical connectors from both sensors.
    3. Use the O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
    4. Install the new oxygen sensors by threading them into place and tightening to the manufacturer's torque specification (typically around 30 lb-ft).
    5. Reconnect the electrical connectors to the sensors.

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

  • Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if applicable).
  • Steps:
    1. Raise the vehicle securely using jack stands.
    2. Inspect the catalytic converter for damage or clogging.
    3. If replacement is needed, disconnect the exhaust pipes from both ends of the catalytic converter.
    4. Cut the exhaust pipes if they are welded.
    5. Install the new catalytic converter, ensuring proper orientation and fitment.
    6. Reconnect the exhaust pipes using clamps or welds as needed.

4. Clear Codes and Test Drive

  • Tools Required: OBD-II scanner.
  • Steps:
    1. Reconnect the negative battery terminal.
    2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s system.
    3. Test drive the vehicle under various conditions to ensure the issue is resolved and 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
  • O2 sensor socket
  • Multimeter
  • Socket set
  • Torque wrench
  • Jack and jack stands
  • Exhaust pipe cutter (if applicable)

Parts Required

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

Additional Information

Error CodeP0420
Component

Exhaust System

Repair Time

2-4 hours

Difficulty

medium

Severity

medium

Tools

7 items

Parts

3 items

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