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

Honda Accord 9th Generation (2013-2017)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0420

3 min read

581 words

Problem Statement

Learn how to diagnose and fix P0420 code in Honda Accord 2013-2017. 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.
•Allow the engine to cool before opening the exhaust system to avoid burns.

Symptoms

•Check engine light illuminated
•Poor fuel economy
•Loss of power during acceleration
•Increased emissions
•Rattling noise from the exhaust system

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' operation by monitoring their voltage output with a multimeter.
4
Test the catalytic converter for restrictions by measuring back pressure.
5
Verify the fuel trim readings to ensure the engine is not running too rich or too 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
•Oxygen sensor socket or wrench
•Socket set
•Torque wrench
•Multimeter
•Safety glasses
•Gloves

Parts Required

•New upstream and downstream oxygen sensors
•New catalytic converter (if replacement is necessary)
•Exhaust gaskets (if required)

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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' operation by monitoring their voltage output with a multimeter.
4
Test the catalytic converter for restrictions by measuring back pressure.
5
Verify the fuel trim readings to ensure the engine is not running too rich or too lean.

Solution

1. Preparation

Gather tools and parts needed for the repair.
Disconnect the negative battery terminal to prevent electrical issues.
Allow the vehicle to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

Locate the oxygen sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
Remove the sensors: Use an oxygen sensor socket or wrench to carefully unscrew each sensor from the exhaust manifold and catalytic converter. Avoid damaging the wiring.
Inspect the sensors: Check the sensors for carbon buildup or damage. If they appear faulty, replace them.
Install new sensors: Apply anti-seize compound on the threads of the new sensors and install them securely. Torque them to the manufacturer’s specifications.

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

Inspect the catalytic converter: Check for physical damage, rattling, or excessive heat discoloration.
Remove the old catalytic converter: Unbolt it from the exhaust system using a socket set. You may need to cut pipes if they are rusted together.
Install the new catalytic converter: Position the new converter in place and secure it with bolts. Ensure to use new gaskets if required. Torque bolts to specifications.
Reinstall any removed exhaust components: Reattach any parts that were removed to access the catalytic converter.

4. Clear Codes and Test Drive

Reconnect the battery: Reconnect the negative terminal and ensure all connections are secure.
Clear the codes: Use the OBD-II scanner to erase the P0420 code from the vehicle's memory.
Test drive the vehicle: Drive the car under various conditions to monitor the performance and ensure the check engine light does not reappear.