FAULTBASE
NEWSASKCars
© 2025 FAULTBASE
All rights reserved.
v2.0.0 • Production
ContactPrivacyImpressum
Home/Cars/Toyota/Highlander/Third Generation (2014-2019)/how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

Toyota Highlander Third Generation (2014-2019)

Severity: highDifficulty: mediumError Code: P04202-4 hours
3 min read
557 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 catalytic converter efficiency issue in Toyota Highlander. 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 engine to cool before opening the exhaust system.

Symptoms

  • •Check engine light illuminated
  • •Decreased fuel efficiency
  • •Rough idling or stalling
  • •Failed emissions test
  • •Unusual exhaust odor (sulfur or rotten egg smell)

Diagnostic Steps

  1. 1Scan for error codes using an OBD-II scanner and confirm P0420 is present.
  2. 2Inspect the exhaust system for leaks, especially before the catalytic converter.
  3. 3Check the condition of the oxygen sensors (upstream and downstream) for proper function.
  4. 4Measure the voltage and output of the upstream and downstream oxygen sensors with a multimeter.
  5. 5Inspect the catalytic converter for physical damage or excessive carbon buildup.
  6. 6Verify that there are no other stored error codes that may affect the catalytic converter performance.

Solution

Solution

1. Preparation

  • Gather necessary tools and parts.
  • Ensure the vehicle is parked on a flat surface and the engine is cool.
  • Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

  • Tools Required: O2 sensor socket, wrench set, penetrating oil.
  • Sub-steps:
    1. Locate the upstream and downstream oxygen sensors (the upstream is typically before the catalytic converter).
    2. Apply penetrating oil on the sensor threads to ease removal.
    3. Disconnect the electrical connectors from both sensors.
    4. Use the O2 sensor socket to remove the old sensors.
    5. Install new oxygen sensors, tightening them to the manufacturer’s specifications (usually 30-45 Nm).
    6. Reconnect the electrical connectors to the new sensors.

3. Inspect and Replace Catalytic Converter

  • Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
  • Sub-steps:
    1. Inspect the catalytic converter for any signs of damage, clogging, or excessive heat discoloration.
    2. If replacement is necessary, disconnect the exhaust pipes by removing the bolts or clamps securing them.
    3. Remove the old catalytic converter from the exhaust system.
    4. Install the new catalytic converter, ensuring proper alignment with the exhaust pipes.
    5. Tighten all bolts to the specified torque (typically 30-40 Nm) to prevent leaks.

4. Reconnect Battery and Reset the Check Engine Light

  • Sub-steps:
    1. Reconnect the negative battery terminal.
    2. Use the OBD-II scanner to clear the P0420 code.

5. Test Drive

  • Take the vehicle for a test drive to ensure the repair was successful and monitor for any reappearance of the check engine light.

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
  • Wrench set
  • Multimeter
  • Torque wrench
  • Exhaust pipe cutter (if necessary)

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 is my Toyota Highlander shuddering when I accelerate

    Learn how to diagnose and fix shuddering during acceleration in Toyota Highlander. Step-by-step guide with diagnostic procedures and repair instructio...

    Component:Drivetrain
    Symptoms
    • •Shuddering or vibration during acceleration
    • •Loss of power or sluggish response
    • +{count} more
  2. why is my Toyota Highlander shaking when I brake

    Learn how to diagnose and fix shaking issues when braking in your Toyota Highlander. Step-by-step guide with diagnostic procedures and repair instruct...

    Component:Brakes
    Symptoms
    • •Vibration felt in the steering wheel during braking
    • •Pulsating brake pedal
    • +{count} more
  3. how to reset the maintenance light on Toyota Highlander Third Generation (2014-2019)

    Learn how to reset the maintenance light on a Toyota Highlander (2014-2019) after maintenance. Step-by-step guide for a quick reset.

    Component:Electrical
    Symptoms
    • •Maintenance light illuminated on the dashboard
    • •Reminder for service displayed on the odometer
    • +{count} more
  4. how to fix Toyota Highlander shuddering when accelerating?

    Learn how to diagnose and fix shuddering during acceleration in Toyota Highlander. Step-by-step guide with diagnostic procedures and repair instructio...

    Component:Transmission
    Symptoms
    • •Shuddering or vibration felt through the steering wheel or chassis during acceleration
    • •Loss of power or sluggish acceleration
    • +{count} more
  5. how to troubleshoot P0301 code on Toyota Highlander Third Generation (2014-2019)

    P0301

    Learn how to diagnose and fix P0301 cylinder 1 misfire in Toyota Highlander (2014-2019). Step-by-step guide with diagnostic procedures and repair inst...

    Component:Engine
    Symptoms
    • •Check engine light illuminated
    • •Rough idle or engine shaking
    • +{count} more
  6. my Toyota Highlander shakes when accelerating what could be wrong

    Learn how to diagnose and fix shaking during acceleration in Toyota Highlander. Step-by-step guide with symptoms, diagnostic steps, and repair instruc...

    Component:Suspension
    Symptoms
    • •Vehicle shakes or vibrates during acceleration
    • •Noticeable vibrations through the steering wheel or seat
    • +{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