FAULTBASE
Error CodesASKCars
© 2026 FAULTBASE
All rights reserved.
v2.0.0 • Production
ContactPrivacyImpressum
How do I troubleshoot a check engine light that keeps coming on in my 2021 Toyota Highlander? - Toyota Highlander
Home/Cars/Toyota/Highlander/Fourth Generation (2020-present)/How do I troubleshoot a check engine light that keeps coming on in my 2021 Toyota Highlander?

How do I troubleshoot a check engine light that keeps coming on in my 2021 Toyota Highlander?

Toyota Highlander Fourth Generation (2020-present)

Error Codes
medium
Difficulty
medium
Severity
Navigation
ProblemSymptomsDiagnosisSolution
ProblemSymptomsDiagnosisSolution
3 min read
546 words

Problem Statement

Learn how to troubleshoot and resolve check engine light issues for your 2021 Toyota Highlander with step-by-step diagnostic and repair instructions.

Affected Component
Engine

Symptoms

  • •Check Engine Light (CEL) illuminated on the dashboard
  • •Rough idling
  • •Decreased fuel efficiency
  • •Unusual engine noises
  • •Performance issues

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
  • •Torque wrench
  • •Basic hand tools (screwdrivers, pliers, wrenches)
  • •Multimeter
  • •Repair manual (specific to 2021 Toyota Highlander)
  • •Safety glasses
  • •Gloves

Additional Information

Affected Component
Engine
Difficulty
medium
Severity
medium
Tools Required
7 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
Troubleshooting a Check Engine Light for a 2021 Toyota Highlander
Tools Required
  • OBD-II Scanner
  • Torque wrench
  • Basic hand tools (screwdrivers, pliers, wrenches)
  • Multimeter
  • Repair manual (specific to 2021 Toyota Highlander)
  • Safety glasses
  • Gloves
Repair Instructions

  1. Addressing Specific Code Issues:

    • Replacing Spark Plugs:
      • Remove the engine cover (if needed).
      • Disconnect the ignition coils and remove them.
      • Use a spark plug socket to remove the old spark plugs and install new ones, torque to specifications (typically around 13 lb-ft for Highlanders).
    • Replacing Oxygen Sensors:
      • Locate the faulty O2 sensor (upstream or downstream as indicated by the code).
      • Disconnect the electrical connector and unscrew the sensor using a wrench.
      • Install the new sensor and reconnect it.
    • Repairing EVAP System:
      • Inspect and replace any cracked hoses in the EVAP system.
      • Test the gas cap; replace if it’s damaged or not sealing properly.

  2. Clearing the Codes

    • After repairs, use the OBD-II scanner to clear the codes.
    • Start the engine and observe if the CEL returns.

  3. Test Drive

    • Take the vehicle for a test drive to ensure that the issue is resolved and the check engine light does not reappear.

  4. Final Check

    • After a few days of driving, recheck the codes with the OBD-II scanner to ensure no new codes have appeared.
Conclusion

If the Check Engine Light continues to illuminate after following these steps, or if you are uncertain about any diagnosis or repair, it is advisable to consult a professional automotive technician or your local Toyota dealer for further assistance.