Signs of a Failing Ignition Coil in the 2020 Toyota Highlander

A failing ignition coil can lead to several performance issues in your 2020 Toyota Highlander. Here are the key symptoms to look out for:

Tools Required

• OBD-II Scanner
• Multimeter
• Torque Wrench
• 10mm Socket and Ratchet
• Screwdriver Set
• Safety Glasses and Gloves

Step 1: Scan for Trouble Codes

1. Connect the OBD-II Scanner to the vehicle’s diagnostic port (usually located under the dashboard).
2. Read and record any trouble codes, particularly those related to ignition misfires (e.g., P0300-P0306).

Step 2: Inspect the Ignition System

1. Visual Inspection: Check for any visible damage to the ignition coils, wiring, or connectors.
2. Check for Corrosion: Look for corrosion on connectors and terminals that could inhibit electrical flow.

Step 3: Test the Ignition Coil

1. Remove the Ignition Coil:

   • Disconnect the battery (negative terminal).
   • Remove any necessary engine covers.
   • Unplug the electrical connector from the ignition coil.
   • Use a 10mm socket to remove the ignition coil from the cylinder head.

2. Measure Resistance:

   • Using a multimeter, set it to the ohms setting.
   • Measure the primary resistance between the positive and negative terminals of the ignition coil. Typical values range from 0.4 to 2 ohms.
   • Measure the secondary resistance between the high voltage terminal and the negative terminal. Values should be between 6,000 to 15,000 ohms.

3. Compare Readings:

   • If the readings fall outside the specified range, the ignition coil is likely faulty.

Step 4: Swap Ignition Coils (if applicable)

1. Swap the Ignition Coil with one from another cylinder (if the engine has multiple coils) to see if the misfire follows the coil.
2. Reinstall and Test: Reconnect the battery and start the engine. If the misfire code changes to the swapped cylinder, the ignition coil is confirmed as faulty.

Repair Instructions

If you determine that the ignition coil is faulty, follow these repair steps:

Step 1: Purchase Replacement Ignition Coil

• Obtain a new ignition coil from a reputable supplier, ensuring it matches the OEM specifications.

Step 2: Installation of New Ignition Coil

1. Install the New Coil:

   • Position the new coil in the cylinder head and secure it using the 10mm socket.
   • Reconnect the electrical connector to the ignition coil.

2. Reattach Any Engine Covers: Replace any covers or components removed during the disassembly.

Step 3: Clear Trouble Codes

• Use the OBD-II scanner to clear any trouble codes stored in the ECU.

Step 4: Test Drive

• Take the vehicle for a test drive to ensure proper operation and verify that the Check Engine Light is no longer illuminated.

Step 5: Final Inspection

• After the test drive, perform a visual inspection to ensure everything is reassembled correctly and there are no leaks or loose connections.

By following these detailed steps, you can diagnose and replace a failing ignition coil in your 2020 Toyota Highlander effectively.