FAULTBASE
Error CodesASKCars
© 2026 FAULTBASE
All rights reserved.
v2.0.0 • Production
ContactPrivacyImpressum
What are the common symptoms of a bad ignition coil in a 2020 Toyota Highlander? - Toyota Highlander
Home/Cars/Toyota/Highlander/Fourth Generation (2020-present)/What are the common symptoms of a bad ignition coil in a 2020 Toyota Highlander?

What are the common symptoms of a bad ignition coil in a 2020 Toyota Highlander?

Toyota Highlander Fourth Generation (2020-present)

Error Codes
2-3 hours
Time
medium
Difficulty
medium
Severity
Error Code: P0300-P0306
Navigation
ProblemSymptomsDiagnosisSolution
ProblemSymptomsDiagnosisSolution
4 min read
739 words

Problem Statement

Learn about the common symptoms of a bad ignition coil in a 2020 Toyota Highlander, diagnostic steps, and repair instructions.

Error Code
P0300-P0306
Affected Component
ignition coil
Estimated Time
2-3 hours

Symptoms

  • •Engine Misfires
  • •Decreased Engine Performance
  • •Poor Fuel Economy
  • •Rough Idling
  • •Difficulty Starting the Engine

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

  • •Multimeter
  • •Socket set
  • •Spark plug socket
  • •OBD-II scanner
  • •Torque wrench

Additional Information

Error Code
P0300-P0306
Affected Component
ignition coil
Estimated Time
2-3 hours
Difficulty
medium
Severity
medium
Tools Required
5 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
Common Symptoms of a Bad Ignition Coil in a 2020 Toyota Highlander

When an ignition coil begins to fail, it can lead to various performance issues in your vehicle. Here are the common symptoms associated with a bad ignition coil in a 2020 Toyota Highlander:

  1. Engine Misfires

    • Symptoms: You may feel the engine hesitating or stumbling during acceleration. The vehicle may shake, and you might hear a rough idle.
    • Diagnostic Indicator: The Check Engine Light may illuminate, and a diagnostic trouble code (DTC) related to a misfire (P0300-P0306) may be stored.

  2. Decreased Engine Performance

    • Symptoms: A noticeable lack of power during acceleration, poor throttle response, and a general decrease in engine performance.
    • Impact: The vehicle may struggle to maintain speed, especially when going uphill or during rapid acceleration.

  3. Poor Fuel Economy

    • Symptoms: Increased fuel consumption without a corresponding increase in driving patterns.
    • Diagnosis: This can occur due to unburned fuel entering the exhaust system, leading to a richer fuel mixture to compensate for the misfire.

  4. Rough Idling

    • Symptoms: The engine may vibrate more than usual while idling, leading to an unstable or rough idle experience.
    • Observation: This may also be accompanied by the sound of the engine running unevenly.

  5. Difficulty Starting the Engine

    • Symptoms: The engine may be hard to start, requiring multiple attempts before it finally starts.
    • Cause: This may be due to the ignition coil not providing the necessary voltage to create a spark.
Repair Instructions

Tools and Materials Required

  • Socket set
  • Torque wrench
  • Multimeter
  • OBD-II scanner
  • New ignition coil(s)
  • New spark plugs (if necessary)
  • Dielectric grease
  • Cleaning solvent (for electrical contacts)

Steps for Replacing the Ignition Coil

  1. Safety Precautions

    • Ensure the vehicle is on a flat surface, and the engine is off. Disconnect the negative battery terminal.

  2. Remove Engine Cover

    • If applicable, remove the plastic engine cover to access the ignition coils.

  3. Disconnect Electrical Connectors

    • Carefully unplug the electrical connector from the ignition coil. Use a small flathead screwdriver to release the locking tab if necessary.

  4. Remove Ignition Coil

    • Unbolt the ignition coil from the engine using the appropriate socket.
    • Pull the ignition coil straight out of the cylinder head.

  5. Install New Ignition Coil

    • Apply a small amount of dielectric grease to the inside of the boot of the new ignition coil to prevent moisture ingress.
    • Insert the new ignition coil into the cylinder head and secure it with the bolt. Tighten to the manufacturer’s specifications.

  6. Reconnect Electrical Connectors

    • Plug the electrical connector back onto the new ignition coil, ensuring it clicks into place.

  7. Reinstall Engine Cover

    • If removed, reinstall the engine cover and secure it as necessary.

  8. Reconnect Battery

    • Reconnect the negative battery terminal.

  9. Start the Engine

    • Start the vehicle and monitor for any misfire codes or performance issues.
    • Check for smooth idling and acceleration.

  10. Clear Codes

  • If any trouble codes were logged, use the OBD-II scanner to clear them and ensure the Check Engine Light remains off.
Conclusion

If the symptoms persist after replacing the ignition coil, further diagnosis may be needed, including checking the fuel system or further inspecting electrical components. Regular maintenance and timely replacement of ignition components can help ensure the optimal performance of your 2020 Toyota Highlander.