Mazda3 Radio Harness Hack

Hacking an aftermarket radio harness to add extra wires

To keep the car as close to factory condition as possible I'll be reusing the factory radio harness. Scosche make an aftermarket wiring kit (part number MA03B) that includes the main wires, but there are a number of wires missing (Steering wheel controls, Illumination, etc). You can add extra wires using the process below.

This is the layout of the factory wiring harness:

Radio harness for 2004 Mazda3

The Scosche MA03B kit includes the following wires:

Scosche MA03B Mazda3

  • Yellow – 12V Constant
  • Red – 12V Accessory
  • Black - Ground
  • Green – Left Rear Speaker (+)
  • Green with Black Stripe Left Rear Speaker (-)
  • White – Left Front Speaker (+)
  • White with Black Stripe – Left Front Speaker (-)
  • Purple – Right Rear Speaker (+)
  • Purple with Black Stripe – Right Rear Speaker (-)
  • Gray – Right Front Speaker (+)
  • Gray with Black Stripe – Right Front Speaker (-)





The missing wires are:

  • Illumination
  • Dimmer
  • Steering Wheel Controls Data A
  • Steering Wheel Controls Data B

To add these wires, you can hack paper clips or breadboard jumper wires to create DIY pins.

Hack together a Car PC Radio Harness with DIY Pins

Drill small holes inside the connector plug (red plug) to fit your DIY pins (green wires) through, then connect into the factory harness (white plug).


Car PC Radio Harness DIY Connected

Slide the rest of the plug over your pins (green wires) and connect as normal.