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Mazda CX-5 Spark Plugs Replacement Guide
How to check or change the spark plugs in a 2017 to 2022 Mazda CX-5 with the Skyactiv-G 2.5L I4 engine.

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2019 CX-5 2.5L I4
Plastic Engine Cover
Release Friction Fasteners
This automotive maintenance tutorial was specifically written to assist owners of the second generation (2017, 2018, 2019, 2020, 2021 and 2022) Mazda CX-5 SUV equipped with the Skyactiv-G 2.5 liter naturally aspirated inline four cylinder engine in checking or changing the spark plugs.

The procedure may be the same or similar for the 2.0L N/A I4, 2.5L turbo I4 and the Skyactiv-D 2.2L twin turbocharged I4 diesel engines.

Owners of other Mazda vehicles such as the CX-3, CX-30, CX-7, CX-9, Mazda3, Mazda6, MX-30, MX-5 Miata, Mazda2, CX-4, CX-8 and BT-50 may also find these DIY instructions to be helpful.

The OEM (original equipment manufacturer) spark plugs in this 2019 CX-5 were marked as part number Denso ZC20HPR11 or Mazda PE5S 18 110 (also known as PE5S-18-110 or PE5S18110).

The new updated OEM spark plug part number is Mazda PE5R-18-110 (also known as PE5R18110 or PE5R 18 110).

A few compatible replacement aftermarket iridium spark plugs with their part numbers are as follows: Autolite XP5682, Bosch 9621, NGK 93501 (LKAR7BIX-11S) and Champion 9019.

The tools and other items needed to complete this procedure include an 8mm socket, a 1/4" drive ratchet, a 14mm spark plug socket (or a 9/16" spark plug socket would also work), a set of 3/8" drive extension bars, a 3/8" drive ratchet and a small tube of dielectric grease.

If the engine is very hot, allow it to cool off for an hour or two before completing this procedure.

Please proceed with caution and at your own risk!

The first two steps are to open the hood and gently pull off the plastic engine cover.

It is held in place a set of four rubber friction fasteners and four pegs (or "spikes").


Engine Cover Removed
Skyactiv-G 2.5L N/A I4
Ignition Coil
Set the plastic engine cover aside in a safe place.

If you have access to compressed air or a wet/dry shop vacuum, thoroughly clean off the top of the engine to help reduce the risk of having debris fall down into the spark plug well.

To further reduce the chance of having something fall down into the cylinder, I recommend only checking or changing one spark plug at a time.

Push In Release Button
Disconnect Power Plug
Loosen Counterclockwise
Push in the release tab on the electrical connector before sliding it straight off the base of the ignition coil.

If you have trouble pushing down the release tab, carefully use a plastic pry bar tool or a flat head screwdriver.

Loosen the single bolt that secures the ignition coil to the valve cover by turning it in the counterclockwise direction with the 8mm socket and a 1/4" drive ratchet.

Remove Single Bolt
Rotate Back & Forth
Remove Ignition Coil
Set the 8mm bolt aside in a safe place.

Gently rotate the ignition coil back and forth a few times to make sure the rubber dust boot is not stuck or "frozen" to the top of the old spark plug.

Lift the ignition coil assembly straight out of the spark plug well and set it aside in a safe place.

Inspect the old ignition coil for any damage or wear.

If you see a CEL (check engine light) or SES (service engine soon) warning indicator on your car's gauge cluster, use an OBDII scanner (also known as an OBD2 scan tool) to check for an ignition coil related DTC (diagnostic trouble code) including P0350, P0351, P0352, P0353 and P0354.

If you need to replace a faulty ignition coil, the OEM part number is Mazda PYFS18100 or PYFS-18-100 (other numbers on the OEM part were H6T61273 K6266 9322A).

A few compatible replacement aftermarket ignition coils part numbers are as follows: Beck/Arnley 178-8527, Delphi GN10625 and Standard Motor Products UF-656.

Ignition Coil Part Number
Old Spark Plug In Well
Spark Plug Socket
Attach your 14mm spark plug socket to a long extension bar and a 3/8" drive ratchet.

I always secure the spark plug socket to the extension bar with some electrical tape to keep it from popping off at the bottom of the well.

Loosen Counterclockwise
Detach Ratchet - Spin Out
Lift Out Old Spark Plug
Lower the socket down into the well and push it on to the top of the old spark plug.

Carefully loosen the old spark plug by turning it in the counterclockwise direction.

If you have trouble loosening the old spark plug due to corrosion (rust), sand or debris, try spraying a very small amount of penetrating oil down into the well.

Allow the penetrating oil to seep into the threads for at least 10 to 15 minutes before attempting to loosen the old plug again.

Once the old spark plug is loose, detach the ratchet.

Spin out the plug the rest of the way by just using the extension bar.

Carefully lift the old spark plug out of the well.

(Your socket should have a rubber piece or a strong magnet to hold the plug securely in place.)

OEM Spark Plug
Spin In New Plug By Hand
Tighten Clockwise

Detach the old spark plug from the socket.

Inspect the old spark plug for any damage, soot, sludge or white ash.

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

If the old spark plugs are dark grey or covered in black soot, the engine might be burning oil and should be checked out by a professional mechanic.

If possible, I recommend buying the OEM iridium tipped spark plugs which are part number Mazda PE5R-18-110 (also known as PE5R18110 or PE5R 18 110).

(Attention - Most spark plug manufacturers recommend that you do NOT use anti-seize lubricant grease on the threads of the new spark plugs since it can easily lead to over tightening.)

If you have a spark plug gap gauge tool, check the gap on the new spark plugs to ensure that they match the manufacturer's specifications on the box.

According to the Mazda CX-5 service manual, the OEM Mazda spark plug gap should be between 0.75mm to 1.10mm (or 0.030" to 0.043").

The shop manual also states that a brand new spark plug should have a gap specification in the narrower range of 0.75mm to 0.85mm (or 0.030" to 0.033").

Push a new spark plug into the socket. (The socket should have a rubber insert or a strong magnet to hold the plug in place.)

Carefully lower the new plug down into the well. Try to avoid hitting the electrode tip on the side walls or the top of the cylinder head.

Spin in the new spark plug in the clockwise direction with just the extension bar until it makes contact with the cylinder head.

I always recommend spinning in the new spark plug by hand to help prevent it from becoming cross threaded.

Continue tightening the new spark plug until it is snug.

If you have a very sensitive and reliable torque wrench, the CX-5 and Mazda6 service manuals list a spark plug torque specification of 12 to 14 lb-ft (or 15 to 20 N-m).

Apply Dielectric Grease
Lower In Ignition Coil
Line Up Bolt Holes

Try to avoid over tightening the spark plugs to prevent from cracking the ceramic portion of the plug or damaging the threads.

Apply a small amount of dielectric grease to the opening at the bottom of the rubber dust boot.

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

Lower the ignition coil in to the spark plug well.

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

Line up the bolt hole in the ignition coil with the bolt hole in the valve cover.

Spin In Ignition Coil Bolt
Tighten Bolt Clockwise
Push On Power Plug
Re-insert the bolt and tighten it in the clockwise direction with the 8mm 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 ignition coil.

You should feel or hear the power plug "click" securely into place.

Lower Engine Cover
Push To Secure Fasteners
Start Engine - Test
Lower the plastic cover down into place over the top of the engine.

Push on the cover to secure the four rubber sockets on to their corresponding pegs.

To test the new spark plugs, start the engine and listen closely for any strange sounds.

If you do hear a weird noise or notice any vibrations, immediately turn off the ignition and double check your work.

Be sure to write down the procedure in your vehicle's service records.

According to the "Schedule Maintenance" chart in the owner's manual the service interval specification for changing the spark plugs is every 75,000 miles (or 120,000 km) for the naturally aspirated Skyactiv-G 2.5L I4 engine.

(If you have the Skyactiv-G 2.5 turbocharged I4 engine, the spark plugs should be changed every 40,000 miles or 64,000 km.)

Please check out all of my 2017-2022 Mazda CX-5 DIY Repair & Maintenance Guides.

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