Which wires give constant, ignition and ground on a 2021 Mazda 3?
On a 2021 Mazda 3, take constant power from the Red wire at the OBD-II port, pin 16, ignition from the interior fuse panel (wire color not published), and ground to the Black wire at the OBD-II port, pin 4. Meter every wire first.
Meter every wire before you tap it. Colors change with trim and build date.
OBD-II port:Under the dash, driver sideBest power spot:OBD-II portSystem voltage:12VIgnition type:Push-button (this page)
Where do I get constant, ignition and ground on a 2021 Mazda 3?
Constant and ground are at the back of the OBD-II port. Ignition is not in the guide.
Option 1 Constant and ground
OBD-II port
Driver side, under the dash.
Constant
Red
OBD-II port, pin 1612V battery feed. Fuse it close to the tap.
Ground
Black
OBD-II port, pin 4Ground wire at the port. Or use bare body metal.
Never tap the start button wires.
Option 2 Ignition
Fuse tap
For switched power.
Ignition
Fuse tap
Interior fuse panelNot in the guide. Find a slot that is dead off and hot on.
Use an add-a-fuse.
From Fortin's install guide for the 2019 to 2023 Mazda 3 with push-button start (guide 88291).
Where are the turn signal, reverse and light wires on a 2021 Mazda 3 for advanced 360 multicam and video telematics installs?
Circuit
Wire color
Location and what it does
Left turnNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Right turnNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Park lightNegative -Not yet checked
Blue
White 12-pin plug at the parking light switch, pin 4Ground when the parking lights are on.
HeadlightNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
ReverseNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Dome lightNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Each chip shows the main insulation color with its stripe. Source: Fortin's install guide for the 2019 to 2023 Mazda 3 with push-button start (guide 88291).
Where are the brake, door, speed and CAN wires on a 2021 Mazda 3 for advanced 360 multicam and video telematics installs?
Circuit
Wire color
Location and what it does
CAN dataDataNot yet checked
Light Blue (high)
Tan (low)
OBD-II port, pins 6 and 14CAN 1 is White (high) and Red (low) on the white 32-pin body control module plug. Never cut or splice the CAN wires.
DoorsNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
BrakePositive +Not yet checked
Gray
Gray 24-pin plug on the body control module, driver kick panel12V when the brake pedal is pressed.
Parking brakeNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Vehicle speedNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Source: Fortin's install guide for the 2019 to 2023 Mazda 3 with push-button start (guide 88291). Wires marked Not found were not in the guide.
Where are the fuse boxes and ground points on a 2021 Mazda 3?
Driver dashOBD-II portConstant, ground, CAN.
Driver kick panelBody control moduleBrake, CAN 1.
Ground pointsPin 4 or body metalNever the battery negative post.
Locations from Fortin's install guide.
Where is the OBD-II port on a 2021 Mazda 3?
OBD II
Diagnostic portOBD-II port: under the dash, driver sidePlug-in GPS trackers and OBD harnesses connect here. Check the port before you plan the install.
Which years share wiring with the 2021 Mazda 3?
This page2021Mazda 3.
Same wiring2019, 2020, 2022, 2023Fortin uses the same guide for these years.
Other years2014, 2015, 2016, 2017, 2018Different wiring. Check the page for your year.
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This page covers the 2021 Mazda 3 compact car with push-button start.
The wire colors come from Fortin's install guide, read wire by wire. Our own team has not yet metered these on a 2021 Mazda 3.
Written by API Signal, fleet GPS and camera installers for 35+ years across Georgia, South Carolina and North Carolina, installing every major telematics and camera brand. Every wire on this page lists its source.
Test every wire with a meter before you tap it
No wiring information is ever guaranteed. Colors and locations change with trim, options and build date, and the manufacturer can change them in the middle of a model year. We share this as a starting point for installers, and you are responsible for confirming every connection on the vehicle in front of you.
Common questions about 2021 Mazda 3 wiring
What wire is constant power on a 2021 Mazda 3?
Red at the OBD-II port, pin 16. 12V battery feed. Meter it before you tap it.
Where is the brake wire on a 2021 Mazda 3?
Gray (positive +) at the gray 24-pin plug on the body control module, driver kick panel. 12V when the brake pedal is pressed. Meter it before you tap it.
Which years share wiring with the 2021 Mazda 3?
2019, 2020, 2022, 2023. Fortin uses the same guide for these years.
Help build this page
Had the panels off on one of these? Show the next installer what you found.
No one has sent photos for the 2021 Mazda 3 yet, so yours could be the first. Every photo, wire color and tip we use goes on this page with your name on it, and it saves the next installer time under the dash.
1. Snap it
The plugs, tap points, fuse boxes and ground points. Phone photos are fine.
2. Send it
Tap "Add yours" at the top of this page. Your tip and your photos go in the same box.
3. See your name on it
We check every tip, then post it here "Compliments of" you, by name.
Compliments of
The installers who helped build this page.
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Founding contributor spot: openThe first installer to confirm a wire or send photos for the 2021 Mazda 3 gets their name here, and it stays here.
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Every tip we use gets a creditThe wire you checked is marked "Checked on a vehicle, compliments of" you.
Want to be famous?
Your name, right on this page, for everyone who uses it to see. Add your tip and your photos in one box.
