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Mazda CX-9 Rear Turn Signal Light Bulb Replacement Guide
How to change a burnt out rear turn signal tail light bulb in a 2nd generation 2016 to 2021 Mazda CX-9 SUV.

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2019 CX-9 Tail Lights
Turn Signal Light Housing
Open Tailgate Door
This automotive maintenance tutorial was specifically written to assist owners of the second generation 2016, 2017, 2018, 2019, 2020 and 2021 Mazda CX-9 SUV in changing a burnt out rear turn signal light bulb (also known as the indicator lamp or "blinker") located in the tail light housing next to the LED brake lights.

Owners of other Mazda vehicles such as the CX-5, CX-3, CX-30, MX-30, CX-8, Mazda8 (MPV), MX-5 Miata, Mazda2 (Demio), Mazda3 (Axela), Mazda6 (Atenza) and Mazda5 (Premacy) may also find these DIY instructions to be helpful.

The compatible replacement amber colored light bulb part number is WY21W (also known as part # 7440NA).

If you would like to have brighter rear turn signal lights that will also last much longer before burning out like the traditional incandescent bulbs, install some WY21W LED units.

The tools needed to access and replace the bulbs include a Phillips head screwdriver, a small flat head screwdriver such as from a precision screwdriver set and possibly also a plastic pry bar tool.

The first two steps are to open the tailgate door for the cargo area and move to the side of the vehicle with the burnt out rear turn signal light bulb.


Plastic Access Cover
Flat Head Screwdriver
Pry Out Plastic Cover
Locate the black plastic rectangular shaped access cover on the inner edge of the tail light housing.

Insert the blade of a small flat head screwdriver into the notch on the bottom edge of the access cover.

Gently pry out the access cover and set it aside in a safe place.

Loosen Counterclockwise
Loosen Top Screw
Two Screws Removed
Locate the two screws that were hidden by the access cover.

Loosen the screws by turning them in the counterclockwise direction with the Phillips head screwdriver.

Set the two screws aside in a safe place.

Plastic Cover & Screws
Gently Loosen Side Edge
Pull Off Tail Light Housing
The tail light housing is still held in place by a slot attached to a pop rivet button head and a plastic peg or "spike" inserted into a grommet.

To loosen these friction fasteners, try pulling the tail light housing straight off the rear corner of the SUV.

If necessary, use a plastic pry bar tool to very gently loosen the friction fasteners.

You can very carefully insert the plastic pry bar tool in between the tail light housing and the painted metal body panel to loosen the two friction fasteners.

Do NOT use excessive force to prevent from cracking the plastic tail light housing.

Turn Over Housing
1/4 Turn Counterclockwise
Turn Signal Bulb Socket
Slide the tail light housing straight off the rear corner of the vehicle.

Turn over the tail light housing to access the bulb socket.

(On this 2019 CX-9 AWD model, the brake or "stop" lights are LED bulbs that should last the lifetime of the vehicle.)

Rotate the base of the rear turn signal light bulb socket 1/4 turn in the counterclockwise direction.

Pull the socket straight out of the tail light housing.

If the old light bulb was recently turned on, be careful when you remove it. The old bulb might still be hot enough to burn your fingers.

Old Light Bulb Removed
OEM Amber Bulb
Push In New Light Bulb
Carefully pull the old light bulb straight out of the socket.

If you have trouble removing the old light bulb, put on some protective gloves and try gently wiggling the light bulb back and forth while pulling it straight out.

Try to avoid using excessive pressure on the old bulb to prevent the glass from breaking and possibly cutting your fingers.

The OEM (original equipment manufacturer) light bulb in this 2019 CX-9 was marked as part number KHA 12V21W WY21W.

Push a new number WY21W wedge base light bulb straight into the socket.

Clean off the incandescent bulb with a paper towel

If you'd like to have brighter rear turn signal lights, install some compatible replacement WY21W LED units.

Empty Bulb Housing
1/4 Turn Clockwise - Lock
Line Up Slot & Pop Rivet
Insert the bulb socket back into the housing and rotate it 1/4 turn in the clockwise direction to secure it into place.

If you installed an LED bulb, I recommend testing the new bulb before you re-attach the tail light housing. To test the new bulb, activate the hazard signal or turn signal.

Tip -  If the new LED bulb doesn't work, try removing it from the socket, rotating it 180 degrees and pushing it back into the socket. Some LED bulbs are "polarized" and will only work when the "+" positive and "-" negative electrical contacts in the correct orientation.

Once you are done replacing the light bulb, line up the tail light housing with the rear corner of the vehicle.

Peg / Spike & Grommet
Push On Light Housing
Tighten Top Screw
Make sure the slot and plastic peg or "spike" on the back side of the tail light housing is aligned with the grommet and pop rivet button head on the rear corner of the SUV.

Slide the tail light housing back into place.

Make sure the front outer corner of the light housing is flush with the painted metal body panel.

Tighten Bottom Screw
Both Screws Secured
Line Up Plastic Cover
Replace the two Phillips head screws by turning them in the clockwise direction until they are snug.

Try to avoid over tightening the screws to prevent from cracking the plastic inner edge of the housing.

Line up the plastic access cover with the inner edge of the tail light housing.

First, re-insert the two tabs on the top edge into the opening.

Pop In Access Panel
Activate Hazard Signals
Test New Light Bulbs
Gently pop in the bottom edge of the access cover.

Make sure the access cover is securely in place.

To test the new rear turn signal light bulbs, either activate the turn signals individually or just press the "Hazard" signal button to turn them both on at the same time.

Don't forget to write down the bulb change in your car's service records.

For more, please check out all of the 2016-2021 Mazda CX-9 DIY Repair & Maintenance Guides.

If you found this guide to be helpful, please consider making a small donation by clicking on the "Donate" button located to the right of this paragraph. Thank you!
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