FAULTBASE
Error CodesASKCars
© 2026 FAULTBASE
All rights reserved.
v2.0.0 • Production
ContactPrivacyImpressum
how to fix P0420 code on Toyota Highlander XU70 (2020-Present) - Toyota Highlander
Home/Cars/Toyota/Highlander/XU70 (2020-Present)/how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

Toyota Highlander XU70 (2020-Present)

Error Codes
2-4 hours
Time
medium
Difficulty
medium
Severity
Error Code: P0420
Navigation
ProblemSymptomsDiagnosisSolution
ProblemSymptomsDiagnosisSolution
3 min read
551 words

Problem Statement

Learn how to diagnose and fix P0420 code related to catalytic converter efficiency in Toyota Highlander XU70. 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 battery before working on electrical systems.
  • •Allow the exhaust system to cool before handling components.

Symptoms

  • •Check engine light illuminated
  • •Decreased fuel efficiency
  • •Poor engine performance or sluggish acceleration
  • •Increased emissions
  • •Possible rotten egg smell from exhaust

Diagnostic Steps

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5

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
  • •Infrared thermometer
  • •Socket set
  • •Safety glasses
  • •Gloves

Parts Required

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

Additional Information

Error Code
P0420
Affected Component
Exhaust System
Estimated Time
2-4 hours
Difficulty
medium
Severity
medium
Tools Required
6 items
Parts Required
3 items

Related Faults

Loading...

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
Solution
1. Preparation
  • Gather tools: OBD-II scanner, multimeter, infrared thermometer, socket set, safety glasses, gloves.
  • Disconnect the negative battery terminal to ensure safety during repairs.
2. Inspect and Replace Oxygen Sensors

  1. Locate the Oxygen Sensors:

    • Find the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.

  2. Remove the Sensors:

    • Use a socket or wrench to carefully unscrew the oxygen sensors from their locations.
    • Store the sensors safely for inspection.

  3. Test the Sensors:

    • Use a multimeter to check the voltage output of each sensor.
    • If the upstream sensor does not fluctuate between 0.1V and 0.9V, it may need replacement.

  4. Install New Sensors:

    • Apply anti-seize compound on the threads of the new sensors.
    • Install the new upstream and downstream oxygen sensors, tightening them to manufacturer specifications.
3. Inspect and Replace Catalytic Converter

  1. Visual Inspection:

    • Check the catalytic converter for any external damage or signs of blockage.

  2. Temperature Test:

    • Use an infrared thermometer to measure the inlet and outlet temperatures of the catalytic converter. A significant difference indicates a failing converter.

  3. Remove the Catalytic Converter:

    • Support the exhaust system as needed.
    • Disconnect the catalytic converter from the exhaust manifold and the rest of the exhaust system using a socket set.

  4. Install New Catalytic Converter:

    • Position the new catalytic converter and secure it with the appropriate fasteners.
    • Reconnect the exhaust system ensuring all gaskets are replaced as necessary.
4. Reconnect Battery and Clear Codes
  • Reconnect the negative battery terminal.
  • Use the OBD-II scanner to clear the P0420 code from the system.