🔧 Highlander - Ignition Coil Replacement

Your Highlander uses 6 individual ignition coils (one per cylinder). Replacing a bad coil can fix misfires, rough idle, and a flashing check engine light. The front bank is easy; the rear bank requires removing the upper intake plenum for access.

Difficulty Level: Intermediate | Estimated Time: 1.0-3.0 hours

---

⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before starting (burn risk).
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts.
• ⚠️ If the check engine light is flashing, avoid driving until repaired (can damage the catalytic converters).
• ⚠️ Keep dirt out of the intake and spark plug wells; cover open ports with clean rags.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 10mm deep socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3" extension
• 6" extension
• Torque wrench (inch-lb)
• Torque wrench (ft-lb)
• Flathead screwdriver
• Needle-nose pliers
• Trim clip remover
• Shop flashlight
• Mechanic gloves
• Safety glasses

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-6
• Upper intake plenum gasket - Qty: 1 (needed for rear bank access)
• Throttle body gasket - Qty: 1 (recommended if throttle body is removed)
• Dielectric grease - Qty: 1 (optional)

---

📋 Before You Begin

• 🅿️ Park on level ground, shift to Park, and set the parking brake.
• 🔋 Disconnect the negative battery terminal using a 10mm socket.
• 🧼 Blow/brush away dust around the coils before removal.
• Torque wrench = tool that tightens to exact spec.
• Dielectric grease = silicone grease for electrical boots.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Lift off the plastic engine cover by pulling straight upward (some covers use grommets).
• If clips are present, pop them using a trim clip remover.

Step 2: Replace front-bank coils (easy access)

• Locate the three coils at the front of the engine.
• Press the connector lock tab and unplug each coil connector by hand. Use a flathead screwdriver gently only if stuck.
• Remove the coil hold-down bolt using a 10mm socket and 1/4" drive ratchet.
• Pull the coil straight upward to remove it from the spark plug well.
• If using grease, apply a pea-sized amount inside the new coil boot. Don’t smear grease on the metal spring.
• Install the new coil by pushing straight down until fully seated.
• Install the hold-down bolt and Torque to 10 Nm (89 in-lb) using a torque wrench (inch-lb).
• Reconnect the electrical connector until it clicks.

Step 3: Gain access to rear-bank coils (upper intake plenum removal)

• Remove the air intake tube:
  • Loosen the hose clamps using a flathead screwdriver.
  • Unclip any small hoses carefully using needle-nose pliers if needed.
  • Lift out the intake tube and set aside.
• Disconnect any vacuum hoses and electrical connectors attached to the upper intake plenum. Use a shop flashlight to confirm nothing is still attached.
• Remove the upper intake plenum mounting bolts/nuts using a 10mm socket, 3/8" drive ratchet, and a 6" extension.
• Lift the plenum off carefully. Cover the exposed intake openings with clean rags immediately.
• Remove and discard the old upper intake plenum gasket.

Step 4: Replace rear-bank coils

• With the plenum removed, locate the three rear coils.
• Unplug the coil connectors by pressing the lock tabs.
• Remove each coil hold-down bolt using a 10mm socket and 1/4" drive ratchet.
• Pull each coil straight up to remove.
• Install the new coils, then install the hold-down bolts and Torque to 10 Nm (89 in-lb) using a torque wrench (inch-lb).
• Reconnect each coil electrical connector until it clicks.

Step 5: Reinstall the upper intake plenum

• Remove the rags covering the intake ports.
• Install the new upper intake plenum gasket in its groove/seating surface.
• Set the upper intake plenum back into place carefully without pinching hoses.
• Start all bolts/nuts by hand first to avoid cross-threading.
• Tighten the plenum fasteners evenly in a crisscross pattern using a 10mm socket and 3/8" drive ratchet.
• Torque to 21 Nm (15 ft-lb) using a torque wrench (ft-lb).
• Reconnect all vacuum hoses and electrical connectors.

Step 6: Reinstall the intake tube and finish up

• Reinstall the air intake tube and tighten clamps using a flathead screwdriver.
• Reconnect the negative battery terminal using a 10mm socket.
• Reinstall the engine cover.

---

✅ After Repair

• 🔎 Start the engine and listen for smooth idle (no shaking).
• 🔎 Check for air leaks: hissing sounds or high idle usually means a loose hose or plenum not seated.
• 🧪 If the check engine light was on, clear codes with a scan tool (recommended) and confirm the misfire does not return.
• 🚗 Take a short test drive and recheck for warning lights.

---

💰 DIY vs Shop Cost

Shop Cost: $450-$1,050 (parts + labor)

DIY Cost: $120-$600 (parts only)

You Save: $330-$450 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-3.0 hours.

---

🎯 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.