Signs of a Failing Ignition Coil in a 2020 Toyota Highlander

The ignition coil is a critical component in the ignition system, responsible for converting the battery's low voltage into the high voltage required to ignite the air-fuel mixture in the engine's cylinders. A failing ignition coil can lead to various symptoms that can affect vehicle performance and drivability. Here are the typical signs you might encounter in a 2020 Toyota Highlander:

Step 1: Visual Inspection

• Check for Physical Damage: Inspect the ignition coils for any visible signs of damage, such as cracks, corrosion, or burnt areas.
• Examine Wiring and Connections: Ensure that all electrical connections to the ignition coils are secure and free from corrosion.

Step 2: Scan for Diagnostic Trouble Codes (DTCs)

• Tools Required: OBD-II scanner
• Procedure:
  1. Connect the OBD-II scanner to the diagnostic port under the dashboard.
  2. Retrieve any stored DTCs related to ignition misfires (e.g., P0300-P0306).
  3. Document the codes and any freeze frame data.

Step 3: Perform a Coil Resistance Test

• Tools Required: Multimeter
• Procedure:
  1. Disconnect the ignition coil connector.
  2. Remove the ignition coil from the engine.
  3. Set the multimeter to ohms.
  4. Measure the primary and secondary resistance of the coil based on the specifications in the service manual (typically around 0.5-2 ohms for primary and 6,000-15,000 ohms for secondary).
  5. Compare your readings to the manufacturer specifications. If they are outside the specified range, the coil may be faulty.

Step 4: Spark Test

• Tools Required: Spark tester
• Procedure:
  1. Reconnect the ignition coil to the connector.
  2. Remove the spark plug and connect the spark tester to the spark plug wire.
  3. Crank the engine and observe if a strong spark is present.
  4. If no spark is observed, the ignition coil or the related circuitry may be faulty.

Repair Instructions

Step 1: Replacement of Ignition Coil

• Tools Required: Ratchet set, socket set, torque wrench, dielectric grease
• Procedure:
  1. Disconnect the Battery: Remove the negative terminal from the battery to prevent electrical shock.
  2. Remove the Engine Cover: If applicable, remove any covers obstructing access to the ignition coils.
  3. Disconnect the Ignition Coil Connector: Carefully disconnect the electrical connector from the faulty ignition coil.
  4. Remove the Ignition Coil: Use a ratchet and appropriate socket to remove the retaining bolt(s) and pull the ignition coil out of the spark plug tube.
  5. Install the New Ignition Coil:
     • Apply a small amount of dielectric grease to the inside of the coil boot to help with installation and prevent moisture entry.
     • Insert the new ignition coil into the spark plug tube and secure it with the retaining bolt(s).
  6. Reconnect the Electrical Connector: Ensure that the connector clicks into place securely.
  7. Reinstall Engine Cover: If removed, reinstall the engine cover.
  8. Reconnect the Battery: Reconnect the negative battery terminal.

Step 2: Clear DTCs and Test Drive

• Tools Required: OBD-II scanner
• Procedure:
  1. Use the OBD-II scanner to clear any stored DTCs from the vehicle’s computer.
  2. Start the vehicle and perform a test drive to ensure that the symptoms have been resolved and that no new fault codes appear.

Conclusion

If you experience any of the symptoms listed, it is crucial to diagnose and address issues with the ignition coil promptly. Ignoring these signs can lead to more severe engine problems and increased repair costs. Always refer to the manufacturer's service manual for specific torque specifications and procedures related to your vehicle.