Not confident with automotive wiring? Have a professional harness builder or tuner do it, or check your work before first power-up. A wiring mistake can damage the ECU, the engine or the car, or start a fire.
Components
| Ref | Kind | Part | Exclude from BOM |
|---|---|---|---|
| MAIN-R | connector | ||
| NEW-BATT | terminal | ||
| NEW-KEYON | terminal | ||
| OEM-1 | connector | ||
| OEM-2 | connector | ||
| SP-0V | splice | ||
| SP-14V | splice | ||
| SP-GND | splice | ||
| SPEEDUINO-A | connector | ||
| SPEEDUINO-PWR | connector |
Create part
Cut list
Lengths need a layout (0 of 36 routed).
| Wire | From / To | Gauge | Signal |
|---|---|---|---|
| W1 | OEM-1-B / SP-14V-1 | 0.85 | ECU power +14V (main relay) |
| W2 | NEW-KEYON-1 / MAIN-R-COIL+ | 0.5 | Relay coil positive (ignition-switched +12V) |
| W3 | NEW-BATT-1 / MAIN-R-IN | 0.85 | Relay contact input (battery + via main fuse) |
| W4 | MAIN-R-COIL- / SP-GND-1 | 0.5 | Relay coil negative (ECU low-side driver) |
| W5 | MAIN-R-OUT / SPEEDUINO-PWR-12V | 0.85 | Relay contact output (switched +12V bus) |
| W6 | OEM-2-A / SP-GND-1 | 0.85 | Power ground |
| W7 | OEM-2-B / SP-GND-1 | 0.85 | Power ground |
| W8 | SP-GND-1 / SPEEDUINO-A-10 | 0.85 | Ground |
| W9 | SP-GND-1 / SPEEDUINO-A-9 | 0.85 | Ground |
| W10 | OEM-2-C / SP-0V-1 | 0.5 | Sensor ground (E2) |
| W11 | OEM-2-D / SP-0V-1 | 0.5 | Sensor ground (E2) |
| W12 | OEM-2-F / SP-0V-1 | 0.5 | MAF ground |
| W13 | SP-0V-1 / SPEEDUINO-A-12 | 0.5 | Ground |
| W14 | SP-0V-1 / SPEEDUINO-A-23 | 0.5 | Ground |
| W15 | OEM-2-K / SPEEDUINO-A-13 | 0.5 | +5V sensor supply |
| W16 | OEM-2-E / SPEEDUINO-A-25 | 0.5 | Crank position (CAS NE) |
| W17 | OEM-2-G / SPEEDUINO-A-24 | 0.5 | Cam position (CAS G) |
| W18 | OEM-1-G / SPEEDUINO-A-7 | 0.5 | Ignition 1 (coils 1+4, wasted spark) |
| W19 | OEM-1-H / SPEEDUINO-A-34 | 0.5 | Ignition 2 (coils 2+3, wasted spark) |
| W20 | OEM-2-U / SPEEDUINO-A-1 | 0.5 | Injector 1 |
| W21 | OEM-2-V / SPEEDUINO-A-2 | 0.5 | Injector 2 |
| W22 | OEM-2-Y / SPEEDUINO-A-3 | 0.5 | Injector 3 |
| W23 | OEM-2-Z / SPEEDUINO-A-5 | 0.5 | Injector 4 |
| W24 | OEM-2-M / SPEEDUINO-A-22 | 0.5 | Throttle position (TPS) |
| W25 | OEM-2-Q / SPEEDUINO-A-19 | 0.5 | Coolant temperature (ECT) |
| W26 | OEM-1-J / SPEEDUINO-A-16 | 0.5 | A/C relay |
| W27 | OEM-1-R / SPEEDUINO-A-15 | 0.5 | Cooling fan relay |
| W28 | OEM-2-S / SPEEDUINO-A-36 | 0.5 | Condenser fan relay |
| W29 | OEM-2-T / SPEEDUINO-A-35 | 0.5 | Fuel pump relay |
| W30 | OEM-1-L / SPEEDUINO-A-37 | 0.5 | Coolant fan relay |
| W31 | OEM-2-L / SPEEDUINO-A-38 | 0.5 | Rear defroster relay |
| W32 | OEM-2-I / SPEEDUINO-A-17 | 0.5 | Tachometer output |
| W33 | OEM-2-N / SPEEDUINO-A-21 | 0.5 | O2 sensor |
| W34 | OEM-2-P / SPEEDUINO-A-20 | 0.5 | Intake air temperature (IAT) |
| W35 | OEM-1-M / SPEEDUINO-A-14 | 0.5 | Vehicle speed |
| W36 | OEM-1-C / SPEEDUINO-A-18 | 0.5 | Starter input (12V while cranking) |
Bill of materials
No wire parts assigned: 36 wires need a wire part.
| Part number | Manufacturer | Description | Qty | Unit | Unit price | Buy |
|---|---|---|---|---|---|---|
| connector2 lines | ||||||
| 174515-6 | TE | AMP Multilock .040/.070 hybrid 22-pin female harness plug (Miata NA/NB ECU) | 1 | ea | Mouser ↗Digi-Key ↗Amazon ↗ | |
| 174516-6 | TE | AMP Multilock .040/.070 hybrid 26-pin female harness plug (Miata NA/NB ECU) | 1 | ea | Mouser ↗Digi-Key ↗Amazon ↗ | |