🔧 Highlander - Ignition Coil Replacement

Replacing an ignition coil means removing the coil that sits on top of a spark plug and installing a new one. On your Highlander, the front bank coils are fairly easy to reach, but the rear bank coils are under the upper intake manifold, so access is more involved.

Difficulty Level: Intermediate | Estimated Time: 1-3 hours

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⚠️ Safety & Precautions

• ⚠️ Your Highlander is a hybrid, so do not touch orange high-voltage cables or hybrid system components.
• ⚠️ Turn the vehicle fully OFF and keep the key fob away from the vehicle while working.
• ⚠️ Disconnect the 12V negative battery cable before removing ignition coils to prevent accidental electrical shorts.
• ⚠️ Work only on a cool engine. The intake manifold, cylinder heads, and exhaust areas can burn skin when hot.
• ⚠️ If removing rear-bank coils, replace disturbed intake gaskets if they are flattened, torn, brittle, or oil-soaked.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 14mm socket
• 3/8-inch ratchet
• 3/8-inch extension set
• 3/8-inch torque wrench
• Flat-blade screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Plastic pick tool
• Magnetic pickup tool
• Clean shop towels
• Masking tape
• Permanent marker
• Nitrile gloves
• Safety glasses
• OBD-II scan tool

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-6
• Upper intake manifold gasket set - Qty: 1, if rear bank coils are removed
• Throttle body gasket - Qty: 1, if throttle body is removed
• Dielectric grease - Qty: 1 small tube

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📋 Before You Begin

• 📍 Park your Highlander on level ground and set the parking brake.
• 🔑 Turn the vehicle OFF. Make sure the READY light is not on.
• 🔋 Disconnect the 12V negative battery cable using a 10mm socket. The 12V battery powers normal vehicle electronics.
• 🧊 Let the engine cool completely before starting.
• 📝 Use masking tape and a permanent marker to label connectors and hoses before disconnecting them.
• 🔎 If you are replacing only one failed coil, use an OBD-II scan tool to identify the misfire cylinder code before removal. Example: P0301 means cylinder 1 misfire.

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🔨 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 clips are tight, use a plastic pick tool gently under the edge to help release it.
• Set the cover aside where it will not be stepped on.
• Pull upward, not sideways.

Step 2: Disconnect the 12V Battery

• Use a 10mm socket and 3/8-inch ratchet to loosen the negative battery terminal clamp.
• Remove the negative cable from the battery post and position it where it cannot spring back.
• A ratchet is the handle that turns sockets; a socket is the removable cup-shaped tool that fits over a bolt or nut.

Step 3: Locate the Ignition Coils

• The ignition coils are black plastic modules mounted on top of the engine, one per cylinder.
• The front bank coils are visible near the radiator side of the engine.
• The rear bank coils are closer to the windshield and require upper intake manifold removal for access.
• If replacing only a front coil, continue to Step 4.
• If replacing a rear coil, continue through the intake removal steps below.

Step 4: Disconnect a Front Ignition Coil Connector

• Press the locking tab on the coil electrical connector with your thumb.
• If the tab is stiff, use a plastic pick tool gently to help depress it.
• Pull the connector straight back; do not pull on the wires.
• Use needle-nose pliers only on the connector body if extra grip is needed.

Step 5: Remove the Front Ignition Coil

• Use a 10mm socket, 3/8-inch extension, and 3/8-inch ratchet to remove the ignition coil hold-down bolt.
• Twist the coil gently by hand to break the rubber boot loose.
• Pull the coil straight upward out of the spark plug tube.
• If the bolt drops, use a magnetic pickup tool to retrieve it.

Step 6: Install the Front Ignition Coil

• Apply a very small amount of dielectric grease inside the end of the coil boot. Dielectric grease is an electrical-safe grease that helps seal out moisture.
• Push the new ignition coil straight down until it fully seats on the spark plug.
• Install the hold-down bolt by hand first to avoid cross-threading.
• Use a 3/8-inch torque wrench with a 10mm socket to tighten the coil bolt to Torque to 8 Nm (71 in-lbs).
• Reconnect the electrical connector until it clicks.

Step 7: Remove Intake Air Ducting for Rear Coil Access

• Use a 10mm socket or flat-blade screwdriver to loosen the air duct hose clamps.
• Use needle-nose pliers to release small hose clamps if equipped.
• Remove the air intake duct and set it aside.
• Cover open intake tubes with clean shop towels so nothing falls inside.

Step 8: Label and Disconnect Rear Intake Connections

• Use masking tape and a permanent marker to label each hose and electrical connector before unplugging it.
• Use a plastic pick tool to release connector locks gently.
• Use needle-nose pliers to move spring clamps back on vacuum or breather hoses.
• Do not force brittle plastic fittings.
• Take photos before unplugging.

Step 9: Remove Upper Intake Manifold Fasteners

• Use a 12mm socket, 3/8-inch extension, and 3/8-inch ratchet to remove the upper intake manifold bolts and nuts.
• Use a 14mm socket if any support bracket fasteners must be removed for clearance.
• Keep bolts organized in the order removed.
• A manifold is the air chamber that distributes air to the engine cylinders.

Step 10: Lift the Upper Intake Manifold

• Carefully lift the upper intake manifold enough to access the rear ignition coils.
• If a hose or connector is still attached, stop and disconnect it using the proper tool from the previous steps.
• Place clean shop towels into exposed intake openings immediately.
• Do not drop bolts, dirt, or tools into the intake ports.

Step 11: Remove the Rear Ignition Coil

• Press the rear coil connector lock and unplug it by hand.
• Use a 10mm socket, 3/8-inch extension, and 3/8-inch ratchet to remove the coil hold-down bolt.
• Twist the coil gently, then pull it straight upward.
• Inspect the spark plug tube for oil or water using a flashlight if available.

Step 12: Install the Rear Ignition Coil

• Apply a tiny amount of dielectric grease inside the new coil boot.
• Push the new coil straight down until seated.
• Start the bolt by hand first.
• Use a 3/8-inch torque wrench with a 10mm socket to tighten the coil bolt to Torque to 8 Nm (71 in-lbs).
• Reconnect the coil connector until it clicks.

Step 13: Reinstall the Upper Intake Manifold

• Remove all clean shop towels from the intake openings before installing the manifold.
• Install new upper intake manifold gaskets if the old gaskets are damaged, flattened, or hardened.
• Lower the upper intake manifold into place by hand.
• Start all bolts and nuts by hand before tightening.
• Use a 3/8-inch torque wrench with a 12mm socket to tighten the upper intake manifold fasteners evenly to Torque to 21 Nm (15 ft-lbs).

Step 14: Reconnect Hoses, Ducting, and Connectors

• Use your labels and photos to reconnect every electrical connector and hose.
• Use needle-nose pliers to return spring clamps to their original positions.
• Use a 10mm socket or flat-blade screwdriver to tighten air duct clamps snugly.
• Do not overtighten plastic intake clamps.

Step 15: Reconnect the 12V Battery and Refit Cover

• Use a 10mm socket and 3/8-inch ratchet to reconnect the 12V negative battery cable.
• Tighten the terminal clamp until secure; do not crush the battery post.
• Push the engine cover straight down until the clips seat.

Step 16: Clear Codes and Test Run

• Use an OBD-II scan tool to clear stored misfire codes.
• Start your Highlander and confirm the READY light comes on normally.
• Let the engine idle when it starts and listen for rough running or hissing vacuum leaks.
• If the engine idles high or runs rough, recheck intake ducting, hoses, and coil connectors.

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✅ After Repair

• ✅ Road test your Highlander gently for 10-15 minutes.
• ✅ Re-scan with the OBD-II scan tool and confirm no misfire codes return.
• ✅ If the check engine light flashes during the test drive, stop driving and recheck the coil connector and spark plug condition.
• ✅ After the engine cools, look over the intake area again for loose hoses or connectors.

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💰 DIY vs Shop Cost

Shop Cost: $250-$900 depending on how many coils are replaced and whether rear-bank access is needed

DIY Cost: $60-$450 parts only

You Save: $190-$450 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-3.0 hours.

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🎯 Ready to get started?

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