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.
Install modifications
Steps on the car itself, outside the harness. Every harness for this car inherits them.
- Re-route the pressure-sensor vacuum hose to the intake manifoldrequired
Re-route the pressure sensor's (Mazda "EGR boost sensor", pin 4AE) vacuum hose directly to the intake manifold, bypassing the EGR boost solenoid. The stock ECU multiplexes baro + MAP through that solenoid: with it off the sensor reads atmosphere, with it energized it reads manifold. After re-routing the sensor reads MAP only, so the standalone needs its own barometric source — its onboard baro sensor if fitted, or a separate baro sensor on a spare analog input. (Alternative, not recommended: keep the hose stock and have the ECU energize the solenoid permanently via a low-side output switched with ignition; this costs an output.)
Why: With the solenoid off (its default) the sensor reads atmospheric pressure, not manifold pressure, so a standalone that uses this sensor as its MAP input would read the wrong value.
Where: EGR boost solenoid and the pressure sensor's vacuum hose (sensor signal 4AE).
Source: Justin Barrera — Miata NA/NB wiring corrections
Components
| Ref | Kind | Part | Exclude from BOM |
|---|---|---|---|
| M190-A | connector | ||
| M190-B | connector | ||
| M190-C | connector | ||
| MAIN-R | connector | ||
| NEW-BATT | terminal | ||
| OEM-2 | connector | ||
| OEM-3 | connector | ||
| OEM-4 | connector | ||
| SP-0V | splice | ||
| SP-14V | splice | ||
| SP-GND | splice |
Create part
Cut list
Lengths need a layout (0 of 75 routed).
| Wire | From / To | Gauge | Signal |
|---|---|---|---|
| W1 | OEM-2-P / SP-14V-1 | 0.85 | ISC valve +14V feed |
| W2 | OEM-4-AF / SP-14V-1 | 0.85 | ECU power +14V (main relay) |
| W3 | OEM-4-D / SP-14V-1 | 0.85 | VVT oil-control solenoid +12V feed |
| W4 | OEM-4-S / MAIN-R-COIL+ | 0.5 | Ignition switch (IG1) sense |
| W5 | NEW-BATT-1 / MAIN-R-IN | 0.85 | Relay contact input (battery + via main fuse) |
| W6 | MAIN-R-COIL- / SP-GND-1 | 0.5 | Relay coil negative (ECU low-side driver) |
| W7 | MAIN-R-OUT / M190-B-H | 0.85 | Relay contact output (switched +12V bus) |
| W8 | MAIN-R-OUT / M190-B-J | 0.85 | Relay contact output (switched +12V bus) |
| W9 | MAIN-R-OUT / M190-B-K | 0.85 | Relay contact output (switched +12V bus) |
| W10 | MAIN-R-OUT / M190-B-L | 0.85 | Relay contact output (switched +12V bus) |
| W11 | OEM-4-AG / M190-A-38 | 0.85 | Constant +12V |
| W12 | OEM-3-A / SP-GND-1 | 0.85 | Power ground |
| W13 | OEM-3-B / SP-GND-1 | 0.85 | Power ground |
| W14 | OEM-4-A / SP-GND-1 | 0.85 | Power ground |
| W15 | SP-GND-1 / M190-B-G | 0.85 | Battery Negative 1 |
| W16 | SP-GND-1 / M190-B-W | 0.85 | Battery Negative 2 |
| W17 | SP-GND-1 / M190-B-X | 0.85 | Battery Negative 3 |
| W18 | SP-GND-1 / M190-B-Y | 0.85 | Battery Negative 4 |
| W19 | SP-GND-1 / M190-B-Z | 0.85 | Battery Negative 5 |
| W20 | SP-GND-1 / M190-B-c | 0.85 | Battery Negative 6 |
| W21 | OEM-4-O / SP-0V-1 | 0.5 | Signal ground |
| W22 | SP-0V-1 / M190-A-18 | 0.5 | Sensor 0V C1 |
| W23 | SP-0V-1 / M190-A-19 | 0.5 | Sensor 0V C2 |
| W24 | SP-0V-1 / M190-A-20 | 0.5 | Sensor 0V C3 |
| W25 | SP-0V-1 / M190-C-14 | 0.5 | Sensor 0V A1 |
| W26 | SP-0V-1 / M190-C-15 | 0.5 | Sensor 0V A2 |
| W27 | SP-0V-1 / M190-C-23 | 0.5 | Sensor 0V B1 |
| W28 | SP-0V-1 / M190-C-30 | 0.5 | Sensor 0V B2 |
| W29 | OEM-4-L / M190-A-16 | 0.5 | +5V sensor supply |
| W30 | OEM-3-Y / M190-C-18 | 0.5 | Crank position (CKP) |
| W31 | OEM-3-V / M190-C-32 | 0.5 | Cam position (CMP) |
| W32 | OEM-4-M / M190-C-51 | 0.5 | Knock sensor |
| W33 | OEM-3-F / M190-C-16 | 0.5 | Ignition 1 (coils 1+4, wasted spark) |
| W34 | OEM-3-I / M190-C-8 | 0.5 | Ignition 2 (coils 2+3, wasted spark) |
| W35 | OEM-2-A / M190-A-11 | 0.5 | Injector 1 |
| W36 | OEM-2-D / M190-A-3 | 0.5 | Injector 2 |
| W37 | OEM-2-G / M190-B-U | 0.5 | Injector 3 |
| W38 | OEM-2-J / M190-A-12 | 0.5 | Injector 4 |
| W39 | OEM-4-X / M190-C-42 | 0.5 | Mass air flow (MAF) |
| W40 | OEM-4-V / M190-C-36 | 0.5 | Throttle position (TPS) |
| W41 | OEM-4-P / M190-C-37 | 0.5 | Coolant temperature (ECT) |
| W42 | OEM-2-B / M190-A-2 | 0.5 | Cooling fan relay |
| W43 | OEM-2-C / M190-B-V | 0.5 | Condenser fan relay |
| W44 | OEM-2-K / M190-A-1 | 0.5 | A/C clutch relay |
| W45 | OEM-2-M / M190-B-b | 0.5 | Fuel pump relay |
| W46 | OEM-3-H / M190-A-5 | 0.5 | Main relay |
| W47 | OEM-2-O / M190-B-S | 0.5 | Fuel pump relay (non-immobiliser) |
| W48 | OEM-3-J / M190-A-48 | 0.5 | Front O2 heater |
| W49 | OEM-3-P / M190-B-a | 0.5 | Rear O2 heater |
| W50 | OEM-2-Q / M190-A-40 | 0.5 | ISC valve low side |
| W51 | OEM-2-E / M190-B-T | 0.5 | EGR valve |
| W52 | OEM-2-F / M190-A-25 | 0.5 | EGR valve |
| W53 | OEM-2-H / M190-A-10 | 0.5 | EGR valve |
| W54 | OEM-2-I / M190-A-47 | 0.5 | EGR valve |
| W55 | OEM-2-N / M190-A-32 | 0.5 | VTCS solenoid (intake butterflies) |
| W56 | OEM-2-R / M190-A-17 | 0.5 | Malfunction indicator lamp (MIL) |
| W57 | OEM-3-C / M190-A-4 | 0.5 | Purge solenoid valve |
| W58 | OEM-3-K / M190-A-26 | 0.5 | EVAP leak detection pump |
| W59 | OEM-3-M / M190-A-33 | 0.5 | Alternator control |
| W60 | OEM-3-U / M190-A-45 | 0.5 | Charge lamp |
| W61 | OEM-4-AH / M190-A-44 | 0.5 | EVAP leak detection pump solenoid valve |
| W62 | OEM-4-R / M190-A-36 | 0.5 | VVT oil-control solenoid (low-side control) |
| W63 | OEM-4-AE / M190-C-35 | 0.5 | Pressure sensor (Mazda: EGR boost sensor) |
| W64 | OEM-4-AA / M190-A-7 | 0.5 | Rear O2 signal |
| W65 | OEM-4-W / M190-A-6 | 0.5 | Front O2 signal |
| W66 | OEM-4-N / M190-C-39 | 0.5 | Intake air temperature (IAT) |
| W67 | OEM-4-AD / M190-C-28 | 0.5 | Fuel level |
| W68 | OEM-3-T / M190-C-25 | 0.5 | Vehicle speed |
| W69 | OEM-3-S / M190-A-21 | 0.5 | Immobiliser |
| W70 | OEM-4-B / M190-A-14 | 0.5 | Brake switch |
| W71 | OEM-4-C / M190-A-30 | 0.5 | Power steering pressure switch |
| W72 | OEM-4-F / M190-A-37 | 0.5 | A/C request |
| W73 | OEM-4-H / M190-C-27 | 0.5 | Neutral switch |
| W74 | OEM-4-I / M190-C-40 | 0.5 | Clutch switch |
| W75 | OEM-4-J / M190-C-47 | 0.5 | VTCS vacuum switch |
Bill of materials
No parts in this harness.