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

569 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 exhaust system issue in Honda Accord 9th Generation. Step-by-step guide with diagnostic procedures and repair instructions.

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 to prevent shorts.
•Allow the exhaust system to cool before inspection or repair to avoid burns.

Symptoms

•Check engine light illuminated
•Decreased fuel efficiency
•Rough idle or stalling
•Failed emissions test
•Increased exhaust emissions
•Unusual exhaust noise

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0420 and check for any additional codes.
2
Inspect the exhaust system for leaks, especially before the catalytic converter.
3
Check the oxygen sensors (upstream and downstream) for proper operation using a multimeter or scan tool.
4
Measure the temperature difference between the inlet and outlet of the catalytic converter to assess its efficiency.
5
Inspect wiring and connectors for the oxygen sensors for any signs of damage or corrosion.
6
Verify the fuel trim readings to ensure the engine is running properly and is not overly rich or lean.

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
•Multimeter
•O2 sensor socket
•Ratchet and socket set
•Torque wrench
•Cutting tool (if necessary)

Parts Required

•Upstream oxygen sensor
•Downstream oxygen sensor
•Catalytic converter
•Exhaust gaskets

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0420 and check for any additional codes.
2
Inspect the exhaust system for leaks, especially before the catalytic converter.
3
Check the oxygen sensors (upstream and downstream) for proper operation using a multimeter or scan tool.
4
Measure the temperature difference between the inlet and outlet of the catalytic converter to assess its efficiency.
5
Inspect wiring and connectors for the oxygen sensors for any signs of damage or corrosion.
6
Verify the fuel trim readings to ensure the engine is running properly and is not overly rich or lean.

Solution

1. Preparation

Gather tools and parts.
Disconnect the battery to prevent electrical shorts during repair.
Raise the vehicle and secure it on jack stands if needed.

2. Inspect and Replace Oxygen Sensors

Tools Required: O2 sensor socket, ratchet, torque wrench.
Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
Remove the upstream O2 sensor by:
1. Disconnecting the electrical connector.
2. Using the O2 sensor socket to unscrew the sensor.
3. Installing the new sensor by reversing the steps, ensuring to torque to manufacturer specifications (typically 30-40 ft-lbs).
Repeat for the downstream O2 sensor if necessary.

3. Inspect and Replace Catalytic Converter

Tools Required: Wrench set, cutting tool (if necessary), exhaust gasket, torque wrench.
Inspect the catalytic converter for physical damage or blockage.
If replacement is needed:
1. Disconnect the exhaust pipes from the catalytic converter.
2. Remove any heat shields covering the catalytic converter.
3. Unbolt the catalytic converter from its mounting brackets.
4. Install the new catalytic converter, ensuring proper alignment.
5. Reattach any exhaust pipes and torque to manufacturer specifications.
6. Replace exhaust gaskets as necessary to prevent leaks.

4. Clear Codes and Test

Reconnect the battery.
Use the OBD-II scanner to clear the P0420 code.
Start the vehicle and conduct a test drive to ensure the issue is resolved.