🔧 Ignition Coils - Replacement

Replacing the ignition coil(s) restores spark delivery to the engine when a coil has failed, causing misfires, rough idle, poor power, or a check engine light. On your Sierra, each cylinder has its own coil, so the repair is straightforward but there is limited room on top of the engine.

Difficulty Level: Beginner | Estimated Time: 1-2 hours

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⚠️ Safety & Precautions

• Let the engine cool fully before starting. Coils sit on hot valve covers.
• Turn the ignition off and remove the key fob from the vehicle area.
• Disconnect the negative battery cable before unplugging coils. This helps prevent accidental shorts.
• Do not pull on the wire harness. Use the connector tab to release each plug.
• If the engine has a misfire, avoid extended driving. A bad coil can damage the catalytic converters.

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🔧 Required Tools

You'll need the following tools for this repair:

• 1/4-inch drive ratchet
• 3/8-inch drive ratchet
• 8mm socket
• 10mm socket
• 6-inch extension
• Trim clip tool
• Small flat-blade pick
• Torque wrench
• Dielectric grease
• Safety glasses
• Mechanic gloves

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1 per failed cylinder
• Ignition coil boot - Qty: 1 per failed cylinder
• Spark plug - Qty: 1 per affected cylinder if due for service
• Dielectric grease - Qty: 1 tube

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📋 Before You Begin

• Park on a level surface and set the parking brake.
• Let the engine cool completely.
• Open the hood and remove any engine cover if equipped.
• Disconnect the negative battery cable before unplugging any coils.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Disconnect battery power

• Use a 10mm socket to loosen the negative battery cable.
• Move the cable aside so it cannot spring back onto the terminal.

Step 2: Remove the engine cover

• If equipped, pull the cover straight up to release it from the mounts.
• If it is tight, use both hands and lift evenly.

Step 3: Access the ignition coils

• Locate the coil on the cylinder you are replacing.
• On the 6.2L V8, the coils sit on top of each valve cover.
• Work on one coil at a time.

Step 4: Disconnect the coil electrical connector

• Use a small flat-blade pick if the connector lock is stiff.
• Press the release tab and pull the connector straight off the coil.
• Do not tug on the wires.

Step 5: Remove the ignition coil

• Use a 10mm socket and ratchet to remove the coil hold-down bolt.
• Pull the coil straight up and out of the spark plug well.
• If it sticks, gently twist while lifting.

Step 6: Inspect the coil boot and spark plug

• Check the rubber boot for cracks, oil, or carbon tracking.
• If the boot is damaged, replace it.
• If the spark plug is worn, replace it now while access is open.

Step 7: Install the new ignition coil

• Apply a small amount of dielectric grease inside the coil boot.
• Push the new coil straight down onto the spark plug.
• Install the hold-down bolt by hand first, then tighten with a 10mm socket.
• Torque to 8 Nm (71 in-lbs).

Step 8: Reconnect the electrical connector

• Push the connector on until it clicks.
• Lightly tug it to make sure it is locked.

Step 9: Reinstall covers and reconnect power

• Reinstall the engine cover by pressing it into place.
• Reconnect the negative battery cable with a 10mm socket.
• Torque to 5 Nm (44 in-lbs) for the battery terminal if you are using a torque wrench.

Step 10: Repeat for any other failed coils

• Replace each bad coil one at a time using the same process.
• Keep connectors and bolts matched to their original locations.

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✅ After Repair

• Start the engine and listen for smooth idle.
• Check that the check engine light is off.
• If the light stays on, scan and clear misfire codes.
• Test drive gently and confirm there is no hesitation under acceleration.

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💰 DIY vs Shop Cost

Shop Cost: $180-$650 (parts + labor)

DIY Cost: $40-$220 (parts only)

You Save: $140-$430 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.8-1.5 hours.

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🎯 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.