🔧 Highlander - Ignition Coil Replacement

Replacing the ignition coils on your Highlander is a straightforward repair. The ignition coils sit on top of the engine and send high voltage to the spark plugs so the engine can fire properly.

This repair is commonly done for misfires, rough idle, poor acceleration, or a check engine light with cylinder misfire codes.

Difficulty Level: Beginner | Estimated Time: 30-60 minutes

---

⚠️ Safety & Precautions

• ⚠️ Work only with the engine completely cool to avoid burns.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils.
• ⚠️ Do not pull on wiring. Pull on the connector body only.
• ⚠️ Replace one coil at a time if you are new to this, so nothing gets mixed up.
• ⚠️ Keep dirt and debris out of the spark plug wells.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8-inch drive ratchet
• 3/8-inch drive extension, 6-inch
• Torque wrench, inch-pound range
• Plastic trim tool
• Needle-nose pliers
• Compressed air nozzle
• OBD2 scan tool
• Battery terminal wrench, 10mm
• Nitrile gloves
• Safety glasses

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1 per failed cylinder
• Ignition coil set - Qty: 1 set of 4 if replacing all coils
• Dielectric grease - Qty: 1 small tube

---

📋 Before You Begin

• Park your Highlander on level ground and shift to Park.
• Set the parking brake.
• Let the engine cool fully before touching the coils or engine cover area.
• Open the hood and support it securely.
• If you have a check engine light, use an OBD2 scan tool first to read misfire codes. OBD2 means the standard diagnostic port system used to read vehicle trouble codes.
• Disconnect the negative battery cable using a 10mm battery terminal wrench.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use both hands to lift the plastic engine cover straight upward.
• If it feels stuck, use a plastic trim tool to gently help release the rubber mounting points.
• Set the cover aside where it will not get stepped on.
• Lift evenly, not from one corner.

Step 2: Locate the Ignition Coils

• The four ignition coils are mounted in a row on top of the engine.
• Each coil has one electrical connector and one small retaining bolt.
• If replacing only one coil, match the failed cylinder from your scan tool code before removing parts.
• Use compressed air nozzle to blow away dust around the coil area before removal.

Step 3: Disconnect the Coil Electrical Connector

• Press the locking tab on the ignition coil connector with your thumb.
• If the tab is hard to press, use a plastic trim tool carefully to help depress it.
• Pull the connector straight back from the coil.
• If needed, use needle-nose pliers only on the connector body, not the wires.
• Never yank the wiring harness.

Step 4: Remove the Ignition Coil Bolt

• Use a 10mm socket, 3/8-inch drive extension, 6-inch, and 3/8-inch drive ratchet to remove the coil retaining bolt.
• Keep the bolt in a safe place.
• Do not drop the bolt into the engine bay.

Step 5: Remove the Old Ignition Coil

• Grip the top of the coil by hand.
• Twist it gently left and right to loosen the rubber boot. The boot is the long rubber part that reaches down to the spark plug.
• Pull the coil straight upward out of the spark plug well.
• Inspect the old coil for oil, water, cracking, or burn marks.
• If oil is present in the spark plug well, the valve cover tube seal may also need repair.

Step 6: Prepare the New Ignition Coil

• Compare the new ignition coil to the old one before installing it.
• Apply a very small amount of dielectric grease inside the end of the rubber boot. Dielectric grease helps keep moisture out of the electrical connection.
• Do not pack the boot full of grease.
• A pea-sized amount is enough.

Step 7: Install the New Ignition Coil

• Slide the new ignition coil straight down into the spark plug well by hand.
• Press down until you feel the boot seat onto the spark plug.
• Make sure the coil mounting ear lines up with the bolt hole.

Step 8: Reinstall the Coil Bolt

• Start the bolt by hand first to avoid cross-threading.
• Use a 10mm socket, 3/8-inch drive extension, 6-inch, and torque wrench, inch-pound range to tighten the bolt.
• Torque to 10 Nm (89 in-lbs).
• Do not overtighten. The coil body and valve cover area can be damaged.

Step 9: Reconnect the Electrical Connector

• Push the electrical connector onto the new ignition coil by hand.
• Listen and feel for a click from the locking tab.
• Lightly tug the connector body to confirm it is locked.

Step 10: Repeat for Other Coils if Needed

• If replacing all four coils, repeat Steps 3 through 9 for each coil.
• Use the same 10mm socket, 3/8-inch drive extension, 6-inch, and torque wrench, inch-pound range for each coil bolt.
• Torque each coil bolt to 10 Nm (89 in-lbs).
• Do one coil at a time.

Step 11: Reinstall the Engine Cover

• Line up the engine cover with its mounting points.
• Press down by hand until the cover seats fully.
• No tool is needed for this step.

Step 12: Reconnect the Battery

• Reconnect the negative battery cable using a 10mm battery terminal wrench.
• Tighten the terminal snugly.
• Do not overtighten the battery terminal clamp.

---

✅ After Repair

• Start your Highlander and let it idle for 1-2 minutes.
• Listen for smooth idle and confirm there is no shaking.
• Use an OBD2 scan tool to clear any stored misfire codes if needed.
• Take a short test drive and check that acceleration feels smooth.
• If the check engine light returns, scan codes again. A remaining misfire may be caused by a spark plug, fuel injector, wiring issue, compression issue, or vacuum leak.

---

💰 DIY vs Shop Cost

Shop Cost: $180-$550 depending on whether one coil or all four are replaced

DIY Cost: $45-$280 for parts only

You Save: $100-$300 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hour.

---

🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.