how to fix P0420 code in Honda Accord 9th Generation (2013-2017)

Honda Accord Eleventh Generation (2023-present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0420

3 min read

561 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 Accord 9th Generation (2013-2017). Step-by-step guide included.

Error Code

P0420

Affected Component

Exhaust System

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the exhaust system to cool before starting work.

Symptoms

•Check engine light illuminated
•Decreased fuel efficiency
•Rough idle or hesitation during acceleration
•Failed emissions test
•Unusual exhaust odor (sulfur smell)

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm the P0420 code and check for any additional codes.
2
Inspect the exhaust system for leaks before the catalytic converter, as this can affect readings.
3
Check the oxygen sensor readings using a multimeter or scanner to ensure they are functioning correctly.
4
Inspect the catalytic converter visually for damage or blockage.
5
Test the catalytic converter's efficiency by measuring the exhaust gas temperature before and after the converter.
6
Verify the engine is running at optimal conditions, checking for misfires or other issues that could affect the catalytic converter.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

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
•Ratchet
•Torque wrench
•Socket set
•Exhaust pipe cutter

Parts Required

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

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm the P0420 code and check for any additional codes.
2
Inspect the exhaust system for leaks before the catalytic converter, as this can affect readings.
3
Check the oxygen sensor readings using a multimeter or scanner to ensure they are functioning correctly.
4
Inspect the catalytic converter visually for damage or blockage.
5
Test the catalytic converter's efficiency by measuring the exhaust gas temperature before and after the converter.
6
Verify the engine is running at optimal conditions, checking for misfires or other issues that could affect the catalytic converter.

Solution

1. Preparation

Gather tools and parts.
Disconnect the battery to avoid electrical shorts.
Allow the exhaust system to cool before starting work.

2. Inspect and Replace Oxygen Sensors (if necessary)

Tools Required: O2 sensor socket, ratchet, torque wrench.
Sub-steps:
1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect the wiring harness from each O2 sensor.
3. Use the O2 sensor socket to remove the sensors.
4. Install new O2 sensors, torque to manufacturer's specifications (typically around 30 ft-lbs).
5. Reconnect the wiring harness.

3. Replace the Catalytic Converter (if necessary)

Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed).
Sub-steps:
1. Locate the catalytic converter in the exhaust system.
2. If applicable, cut the exhaust pipe before and after the catalytic converter using an exhaust pipe cutter.
3. Remove the old catalytic converter by unbolting it from the exhaust manifold and the exhaust pipe.
4. Install the new catalytic converter, ensuring proper orientation.
5. Bolt the converter in place and torque to manufacturer's specifications (typically around 30-40 ft-lbs).
6. If cut, use appropriate exhaust clamps to secure the pipe connections.

4. Clear Codes and Test Drive

Sub-steps:
1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code.
3. Test drive the vehicle to ensure the check engine light does not reappear.