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Toyota Highlander Spark Plugs Replacement Guide
How to check or change the spark plugs in a 3rd generation 2014 to 2018 Toyota Highlander with the 3.5L V6 engine.

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2017 Highlander 3.5L V6
Pull Off Engine Cover
Rubber Cover Removed
This automotive maintenance tutorial was specifically written to assist owners of the third generation (2014, 2015, 2016, 2017, 2018 and probably also the 2019 and 2020 model years) Toyota Highlander SUV in checking or changing the spark plugs in the 2GR-FE or 2GR-FKS 3.5 liter V6 engine.

Owners of other Toyota, Lexus and Scion vehicles such as the 4Runner, Avalon, 86, C-HR, Camry, Corolla, iM, Land Cruiser, Mirai, Prius, RAV4, Sequoia, Sienna, Tacoma, Tundra, Yaris, FR-S, xB,  xD, tC, xA, CT 200h, ES 250, ES 300, ES 330, ES 350, IS 250, IS 350, RX 300, GS 250, NX 300 and RX 350.

The OEM iridium spark plugs in this 2017 Highlander were part number Denso FK20HBR8 (also known as "3491").

The tools needed to complete this procedure include a 10mm socket with a 1/4" drive ratchet, a 5/8" spark plug socket with an extension bar and a 3/8" drive ratchet and a tube of dielectric grease.


A few other compatible replacement spark plugs with their part numbers include the following: Bosch 9603 Iridium, Bosch 8101 Platinum, Autolite APP5325 and Bosch 6724 Platinum.
2GR-FKS Engine
Rear Three Spark Plugs
Front Three Spark Plugs
The first two steps are to open the hood and then pull off the rubber engine cover.

Set the engine cover aside in a safe place.

In order to check or change the three spark plugs on the back side of the engine, you'll need some extension bars and also a universal swivel joint.

Be sure to allow the engine to cool off before working on the rear of the engine.

The front three ignition coils and spark plugs are very easy to access.

I recommend only checking or changing one spark plug at a time to help prevent from having debris fall down into the cylinder block.

Push In Release Tab
Disconnect Electrical Connector
Loosen Counterclockwise
Gently squeeze the release tab on the electrical connector before sliding it straight off the ignition coil housing.

Loosen the single bolt that secures the ignition coil to the top of the engine by turning it in the counterclockwise direction with a 10mm socket and a 1/4" drive ratchet.

Remove Single Bolt
Pull Out Ignition Coil
Part # 90919-A2013
Spin out the bolt and set it aside in a safe place.

Carefully pull the ignition coil straight out of the spark plug well.

If you trouble removing the ignition coil, try gently rotating it back and worth while wiggling it before pulling it straight out. The rubber boot at the bottom of the ignition coil might be stuck or "frozen" to the top of the old spark plug.

If your OBD II (or OBD 2) code scanner displays an ignition coil related error code or DTC (diagnostic trouble code) such as P0351, P0352, P0353, P0354, P0355 or P0356, you may need to replace a faulty ignition coil.

The OEM ignition coil part number is Toyota / DE Diamond Electric 90919-A2013.

Two other compatible replacement ignition coils with their part numbers are as follows: Wells C1601 and Standard Motor Products UF-487.

Spark Plug Well
Attach 5/8" Socket
Loosen Counterclockwise
Attach the 5/8" spark plug socket to a long 6" or 9" extension bar and a 3/8" drive ratchet.

I like to secure the socket to the extension bar with some packing tape to prevent it from popping off and become stuck in the spark plug well.

Lower the socket down into the well and push it down on to the top of the old spark plug.

Loosen the old spark plug by turning it in the counterclockwise direction.

If you have trouble loosening the old spark plug, do not use excessive force to prevent from cracking the ceramic portion of the plug. You could try spraying a very small amount of penetrating oil such as Liquid Wrench or PB Blaster down into the spark plug well and wait about 10 to 15 minutes for it to penetrate the threads.


Spin Out Old Spark Plug
Old Spark Plug Removed
Inspect Old Spark Plug
Once the old spark plug is loose, detach the ratchet from the extension bar.

Spin out the old spark plug the rest of the way by hand.

Pull the old spark plug out of the socket.

Inspect both ends of the old spark plug.

If the electrode end of the old spark plug looks ashy white, the plugs may have been exposed to high temperatures due to engine overheating or they may be the incorrect heat range for your driving conditions or environment.

On the other hand, if the old spark plug is grey or covered in dark black soot, the engine might be burning oil and should be inspected by a professional mechanic.

The OEM spark plugs in this 2017 Highlander were the Denso FK20HBR8 (3491) iridium.

Spin In New Spark Plug
Tighten Clockwise
Apply Dielectric Grease
The new spark plugs should be pre-gapped at the factory. If you have a spark plug gap gauge, you can double check the gap.

Push the new spark plug into the socket.

Lower the new spark plug into the well and spin it a few turns in the clockwise direction by hand to prevent it from becoming cross threaded.

Tighten the new spark plug in the clockwise direction with the 5/8" socket, an extension bar and the 3/8" drive ratchet to just past the point when you feel the crush washer collapse.

If you are re-installing the old spark plug, just tighten it to a fraction of a turn past finger tight.

Double check that the spark plug is tight before moving on to the next steps.

Apply some dielectric grease to the opening in the rubber dust boot at the bottom of the ignition coil.

The dielectric grease will help keep out debris and moisture to help ensure a reliable electrical connection.

Lower In Ignition Coil
Rotate - Spread Grease
Replace 10mm Bolt
Lower the ignition coil down into the spark plug well.

Rotate the ignition coil back and forth a few times to help spread the dielectric grease.

Line up the bolt hole in the ignition coil housing with the corresponding bolt hole in the top of the engine.

Spin in the 10mm bolt a few turns by hand in the clockwise direction to prevent it from becoming cross threaded.

Spin In Clockwise
Tighten Ignition Coil Bolt
Push On Power Plug
Tighten the ignition coil bolt in the clockwise direction with the 10mm socket and a 1/4' drive ratchet until it is snug.

Try to avoid over tightening the bolt to prevent from cracking the plastic ignition coil housing.

Push the electrical connector straight on to the base of the ignition coil until it clicks securely into place.

Spark Plugs Replaced
Lower Engine Cover
Engine Cover Replaced
Lower the foam rubber engine cover down into place.

Push on the cover to secure the friction fasteners to the metal pegs on the top of the engine.

Be sure to record the spark plug change in your vehicle's service records.

Please check out all of my 2014-2018 Toyota Highlander DIY Repair & Maintenance Guides.

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