MX-5 Miata NB2 2001-05 (BP-Z3, VVT; excludes Mazdaspeed) → Speeduino Speeduino v0.4 (auto)
Before you start
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
| Status | draft · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | 2: read the Findings page before cutting any wire |
| Size of the job | 35 wires · 6 connectors · 0 part lines |
| Tools | Crimp and extraction tools for each terminal family (see Connectors) · wire strippers · multimeter · heat gun + heat-shrink |
| Order of work | 1. Check every part against the parts list. 2. Cut and label every wire (labels: Export → Wire labels). 3. Crimp and pin connector by connector, ticking the build checklist. 4. Run the bench test with nothing plugged in and the battery disconnected. 5. Only then connect the ECU and power up. |
Build checklist
Tick each box as you go. Continuity: meter from end to end, expect under 1 Ω.
| Wire | From | To | Gauge | Colour | Cut | Label | Crimp A | Crimp B | Pin A | Pin B | Continuity |
|---|---|---|---|---|---|---|---|---|---|---|---|
| W1 | OEM-3-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-3-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | OEM-4-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-4-O | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | OEM-4-L | SPEEDUINO-A-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-3-Y | SPEEDUINO-A-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-3-V | SPEEDUINO-A-24 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | OEM-3-F | SPEEDUINO-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-3-I | SPEEDUINO-A-34 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-2-A | SPEEDUINO-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-2-D | SPEEDUINO-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-2-G | SPEEDUINO-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-2-J | SPEEDUINO-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-2-B | SPEEDUINO-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-2-C | SPEEDUINO-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-2-K | SPEEDUINO-A-36 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-2-M | SPEEDUINO-A-35 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-3-H | SPEEDUINO-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-3-J | SPEEDUINO-A-38 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-3-P | SPEEDUINO-A-31 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-2-Q | SPEEDUINO-A-32 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-2-E | SPEEDUINO-A-29 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-2-F | SPEEDUINO-A-30 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-3-O | SPEEDUINO-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-4-AE | SPEEDUINO-A-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-4-V | SPEEDUINO-A-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-4-AA | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-4-P | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-4-N | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-3-T | SPEEDUINO-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-3-S | SPEEDUINO-A-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ |
Bench test (before first power-up)
Pre-power install steps (make these cuts/modifications on the car first, then verify the checks below): Re-route the pressure-sensor vacuum hose to the intake manifold.
Battery disconnected, ECU and every sensor unplugged. Meter on resistance. Each pair below must read open (OL): a reading means a pinched wire, a stray strand or a mis-pinned cavity. Then check continuity of every wire (last column of the build checklist).
| # | Probe A | Probe B | Expect | Why | Reading |
|---|---|---|---|---|---|
| 1 | SPEEDUINO-A-13 | SPEEDUINO-A-12 | open (OL) | 5 V sensor reference must not touch sensor ground | |
| 2 | SPEEDUINO-A-10 | SPEEDUINO-A-13 | open (OL) | power ground must not touch 5 V sensor reference |
If any reading doesn't match, stop and get help before powering up.
Revisions
| Rev | Label | By | Date |
|---|---|---|---|
| No revisions yet. | |||
Schematic
Connectors
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Injector 1 | — | W14 | — | 0.5 | SPEEDUINO-A-1 | — | — | — |
| B | Cooling fan relay | — | W18 | — | 0.5 | SPEEDUINO-A-16 | — | — | — |
| C | Condenser fan relay | — | W19 | — | 0.5 | SPEEDUINO-A-15 | — | — | — |
| D | Injector 2 | — | W15 | — | 0.5 | SPEEDUINO-A-2 | — | — | — |
| E | EGR valve | — | W26 | — | 0.5 | SPEEDUINO-A-29 | — | — | — |
| F | EGR valve | — | W27 | — | 0.5 | SPEEDUINO-A-30 | — | — | — |
| G | Injector 3 | — | W16 | — | 0.5 | SPEEDUINO-A-3 | — | — | — |
| H | EGR valve | — | — | — | — | — | — | — | — |
| I | EGR valve | — | — | — | — | — | — | — | — |
| J | Injector 4 | — | W17 | — | 0.5 | SPEEDUINO-A-5 | — | — | — |
| K | A/C clutch relay | — | W20 | — | 0.5 | SPEEDUINO-A-36 | — | — | — |
| M | Fuel pump relay | — | W21 | — | 0.5 | SPEEDUINO-A-35 | — | — | — |
| N | VTCS solenoid (intake butterflies) | — | — | — | — | — | — | — | — |
| P | ISC valve +14V feed | — | — | — | — | — | — | — | — |
| Q | ISC valve low side | — | W25 | — | 0.5 | SPEEDUINO-A-32 | — | — | — |
| R | Malfunction indicator lamp (MIL) | — | — | — | — | — | — | — | — |
OEM-3
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W1 | — | 0.85 | SP-GND-1 | — | — | — |
| B | Power ground | — | W2 | — | 0.85 | SP-GND-1 | — | — | — |
| D | EGR boost solenoid | — | — | — | — | — | — | — | — |
| E | Charcoal canister purge | — | — | — | — | — | — | — | — |
| F | Ignition 1 (coils 1+4, wasted spark) | — | W12 | — | 0.5 | SPEEDUINO-A-7 | — | — | — |
| H | Main relay | — | W22 | — | 0.5 | SPEEDUINO-A-37 | — | — | — |
| I | Ignition 2 (coils 2+3, wasted spark) | — | W13 | — | 0.5 | SPEEDUINO-A-34 | — | — | — |
| J | Front O2 heater | — | W23 | — | 0.5 | SPEEDUINO-A-38 | — | — | — |
| M | Alternator control | — | — | — | — | — | — | — | — |
| O | Tachometer output | — | W28 | — | 0.5 | SPEEDUINO-A-17 | — | — | — |
| P | Rear O2 heater | — | W24 | — | 0.5 | SPEEDUINO-A-31 | — | — | — |
| S | Immobiliser | — | W35 | — | 0.5 | SPEEDUINO-A-18 | — | — | — |
| T | Vehicle speed | — | W34 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| U | Charge lamp | — | — | — | — | — | — | — | — |
| V | Cam position (CMP) | — | W11 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| Y | Crank position (CKP) | — | W10 | — | 0.5 | SPEEDUINO-A-25 | — | — | — |
OEM-4
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W3 | — | 0.85 | SP-GND-1 | — | — | — |
| AA | Rear O2 signal | — | W31 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| AD | Fuel level | — | — | — | — | — | — | — | — |
| AE | Pressure sensor (Mazda: EGR boost sensor) | — | W29 | — | 0.5 | SPEEDUINO-A-11 | — | — | — |
| AF | ECU power +14V (main relay) | — | — | — | — | — | — | — | — |
| AG | Constant +12V | — | — | — | — | — | — | — | — |
| B | Brake switch | — | — | — | — | — | — | — | — |
| C | Power steering pressure switch | — | — | — | — | — | — | — | — |
| D | VVT oil-control solenoid | — | — | — | — | — | — | — | — |
| F | A/C request | — | — | — | — | — | — | — | — |
| H | Neutral switch | — | — | — | — | — | — | — | — |
| I | Clutch switch | — | — | — | — | — | — | — | — |
| J | VTCS vacuum switch | — | — | — | — | — | — | — | — |
| L | +5V sensor supply | — | W9 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
| M | Knock sensor | — | — | — | — | — | — | — | — |
| N | Intake air temperature (IAT) | — | W33 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
| O | Signal ground | — | W6 | — | 0.5 | SP-0V-1 | — | — | — |
| P | Coolant temperature (ECT) | — | W32 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| V | Throttle position (TPS) | — | W30 | — | 0.5 | SPEEDUINO-A-22 | — | — | — |
| W | Front O2 signal | — | — | — | — | — | — | — | — |
| X | Mass air flow (MAF) | — | — | — | — | — | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W6 | — | 0.5 | OEM-4-O | — | — | — |
| 1 | — | — | W7 | — | 0.5 | SPEEDUINO-A-12 | — | — | — |
| 1 | — | — | W8 | — | 0.5 | SPEEDUINO-A-23 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-3-A | — | — | — |
| 1 | — | — | W2 | — | 0.85 | OEM-3-B | — | — | — |
| 1 | — | — | W3 | — | 0.85 | OEM-4-A | — | — | — |
| 1 | — | — | W4 | — | 0.85 | SPEEDUINO-A-10 | — | — | — |
| 1 | — | — | W5 | — | 0.85 | SPEEDUINO-A-9 | — | — | — |
SPEEDUINO-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Injector 1 | — | W14 | — | 0.5 | OEM-2-A | — | — | — |
| 10 | Ground | — | W4 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | MAP sensor (0-5V) | — | W29 | — | 0.5 | OEM-4-AE | — | — | — |
| 12 | Ground | — | W7 | — | 0.5 | SP-0V-1 | — | — | — |
| 13 | 5V | — | W9 | — | 0.5 | OEM-4-L | — | — | — |
| 14 | Proto area 1 (flex fuel) | — | W34 | — | 0.5 | OEM-3-T | — | — | — |
| 15 | Proto area 2 (fan) | — | W19 | — | 0.5 | OEM-2-C | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | W18 | — | 0.5 | OEM-2-B | — | — | — |
| 17 | Proto area 4 (tachometer) | — | W28 | — | 0.5 | OEM-3-O | — | — | — |
| 18 | Proto area 5 (clutch) | — | W35 | — | 0.5 | OEM-3-S | — | — | — |
| 19 | Coolant temp (CLT) | — | W32 | — | 0.5 | OEM-4-P | — | — | — |
| 2 | Injector 2 | — | W15 | — | 0.5 | OEM-2-D | — | — | — |
| 20 | Inlet air temp (IAT) | — | W33 | — | 0.5 | OEM-4-N | — | — | — |
| 21 | O2 sensor | — | W31 | — | 0.5 | OEM-4-AA | — | — | — |
| 22 | TPS input | — | W30 | — | 0.5 | OEM-4-V | — | — | — |
| 23 | Ground | — | W8 | — | 0.5 | SP-0V-1 | — | — | — |
| 24 | Cam input / VR2+ | — | W11 | — | 0.5 | OEM-3-V | — | — | — |
| 25 | Crank input / VR1+ | — | W10 | — | 0.5 | OEM-3-Y | — | — | — |
| 26 | VR2- | — | — | — | — | — | — | — | — |
| 27 | VR1- | — | — | — | — | — | — | — | — |
| 28 | 5V | — | — | — | — | — | — | — | — |
| 29 | Idle stepper 2B | — | W26 | — | 0.5 | OEM-2-E | — | — | — |
| 3 | Injector 3 | — | W16 | — | 0.5 | OEM-2-G | — | — | — |
| 30 | Idle stepper 2A | — | W27 | — | 0.5 | OEM-2-F | — | — | — |
| 31 | Idle stepper 1A | — | W24 | — | 0.5 | OEM-3-P | — | — | — |
| 32 | Idle stepper 1B | — | W25 | — | 0.5 | OEM-2-Q | — | — | — |
| 33 | Ignition 3 | — | — | — | — | — | — | — | — |
| 34 | Ignition 2 | — | W13 | — | 0.5 | OEM-3-I | — | — | — |
| 35 | Boost | — | W21 | — | 0.5 | OEM-2-M | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | W20 | — | 0.5 | OEM-2-K | — | — | — |
| 37 | PWM idle | — | W22 | — | 0.5 | OEM-3-H | — | — | — |
| 38 | VVT | — | W23 | — | 0.5 | OEM-3-J | — | — | — |
| 5 | Injector 4 | — | W17 | — | 0.5 | OEM-2-J | — | — | — |
| 7 | Ignition 1 | — | W12 | — | 0.5 | OEM-3-F | — | — | — |
| 8 | Ignition 4 | — | — | — | — | — | — | — | — |
| 9 | Ground | — | W5 | — | 0.85 | SP-GND-1 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-2-A | Injector 1 | injector_out | SPEEDUINO-A-1 | Injector 1 | injector_out | single_source | |
| OEM-2-B | Cooling fan relay | low_side_out | SPEEDUINO-A-16 | Proto area 3 (fuel pump) | low_side_out | single_source | |
| OEM-2-C | Condenser fan relay | low_side_out | SPEEDUINO-A-15 | Proto area 2 (fan) | low_side_out | single_source | |
| OEM-2-D | Injector 2 | injector_out | SPEEDUINO-A-2 | Injector 2 | injector_out | single_source | |
| OEM-2-E | EGR valve | low_side_out | SPEEDUINO-A-29 | Idle stepper 2B | hbridge_out | single_source | |
| OEM-2-F | EGR valve | low_side_out | SPEEDUINO-A-30 | Idle stepper 2A | hbridge_out | single_source | |
| OEM-2-G | Injector 3 | injector_out | SPEEDUINO-A-3 | Injector 3 | injector_out | single_source | |
| OEM-2-H | EGR valve | low_side_out | — | — | — | single_source | |
| OEM-2-I | EGR valve | low_side_out | — | — | — | single_source | |
| OEM-2-J | Injector 4 | injector_out | SPEEDUINO-A-5 | Injector 4 | injector_out | single_source | |
| OEM-2-K | A/C clutch relay | low_side_out | SPEEDUINO-A-36 | Idle 2 (3-wire idle) | low_side_out | single_source | |
| OEM-2-M | Fuel pump relay | low_side_out | SPEEDUINO-A-35 | Boost | low_side_out | single_source | |
| OEM-2-N | VTCS solenoid (intake butterflies) | low_side_out | — | — | — | single_source | |
| OEM-2-P | ISC valve +14V feed | power_in | — | — | — | single_source | |
| OEM-2-Q | ISC valve low side | low_side_out | SPEEDUINO-A-32 | Idle stepper 1B | hbridge_out | single_source | |
| OEM-2-R | Malfunction indicator lamp (MIL) | low_side_out | — | — | — | single_source | |
| OEM-3-A | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-3-B | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-3-D | EGR boost solenoid | — | — | — | — | single_source | |
| OEM-3-E | Charcoal canister purge | low_side_out | — | — | — | single_source | |
| OEM-3-F | Ignition 1 (coils 1+4, wasted spark) | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | single_source | |
| OEM-3-H | Main relay | low_side_out | SPEEDUINO-A-37 | PWM idle | low_side_out | single_source | |
| OEM-3-I | Ignition 2 (coils 2+3, wasted spark) | ignition_out | SPEEDUINO-A-34 | Ignition 2 | ignition_out | single_source | |
| OEM-3-J | Front O2 heater | low_side_out | SPEEDUINO-A-38 | VVT | low_side_out | single_source | |
| OEM-3-M | Alternator control | low_side_out | — | — | — | single_source | |
| OEM-3-O | Tachometer output | tacho_out | SPEEDUINO-A-17 | Proto area 4 (tachometer) | tacho_out | single_source | |
| OEM-3-P | Rear O2 heater | low_side_out | SPEEDUINO-A-31 | Idle stepper 1A | hbridge_out | single_source | |
| OEM-3-S | Immobiliser | digital_in | SPEEDUINO-A-18 | Proto area 5 (clutch) | digital_in | single_source | |
| OEM-3-T | Vehicle speed | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | single_source | |
| OEM-3-U | Charge lamp | low_side_out | — | — | — | single_source | |
| OEM-3-V | Cam position (CMP) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | single_source | |
| OEM-3-Y | Crank position (CKP) | trigger_in | SPEEDUINO-A-25 | Crank input / VR1+ | trigger_in | single_source | |
| OEM-4-A | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-4-AA | Rear O2 signal | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | single_source | |
| OEM-4-AD | Fuel level | analog_in | — | — | — | single_source | |
| OEM-4-AE | Pressure sensor (Mazda: EGR boost sensor) | analog_in | SPEEDUINO-A-11 | MAP sensor (0-5V) | analog_in | corroborated | |
| OEM-4-AF | ECU power +14V (main relay) | power_in | — | — | — | single_source | |
| OEM-4-AG | Constant +12V | power_in | — | — | — | single_source | |
| OEM-4-B | Brake switch | digital_in | — | — | — | single_source | |
| OEM-4-C | Power steering pressure switch | digital_in | — | — | — | single_source | |
| OEM-4-D | VVT oil-control solenoid | low_side_out | — | — | — | single_source | |
| OEM-4-F | A/C request | digital_in | — | — | — | single_source | |
| OEM-4-H | Neutral switch | digital_in | — | — | — | single_source | |
| OEM-4-I | Clutch switch | digital_in | — | — | — | single_source | |
| OEM-4-J | VTCS vacuum switch | digital_in | — | — | — | single_source | |
| OEM-4-L | +5V sensor supply | vref | SPEEDUINO-A-13 | 5V | vref | single_source | |
| OEM-4-M | Knock sensor | knock_in | — | — | — | single_source | |
| OEM-4-N | Intake air temperature (IAT) | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | single_source | |
| OEM-4-O | Signal ground | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | single_source | |
| OEM-4-P | Coolant temperature (ECT) | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | single_source | |
| OEM-4-V | Throttle position (TPS) | analog_in | SPEEDUINO-A-22 | TPS input | analog_in | single_source | |
| OEM-4-W | Front O2 signal | lambda_nb_in | — | — | — | single_source | |
| OEM-4-X | Mass air flow (MAF) | analog_in | — | — | — | single_source |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-3-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W2 | OEM-3-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W3 | OEM-4-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W4 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | no route | Ground | — | |
| W5 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | no route | Ground | — | |
| W6 | OEM-4-O | SP-0V-1 | 0.5 | no route | Signal ground | — | |
| W7 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | no route | Ground | — | |
| W8 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | no route | Ground | — | |
| W9 | OEM-4-L | SPEEDUINO-A-13 | 0.5 | no route | +5V sensor supply | — | |
| W10 | OEM-3-Y | SPEEDUINO-A-25 | 0.5 | no route | Crank position (CKP) | — | |
| W11 | OEM-3-V | SPEEDUINO-A-24 | 0.5 | no route | Cam position (CMP) | — | |
| W12 | OEM-3-F | SPEEDUINO-A-7 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W13 | OEM-3-I | SPEEDUINO-A-34 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W14 | OEM-2-A | SPEEDUINO-A-1 | 0.5 | no route | Injector 1 | — | |
| W15 | OEM-2-D | SPEEDUINO-A-2 | 0.5 | no route | Injector 2 | — | |
| W16 | OEM-2-G | SPEEDUINO-A-3 | 0.5 | no route | Injector 3 | — | |
| W17 | OEM-2-J | SPEEDUINO-A-5 | 0.5 | no route | Injector 4 | — | |
| W18 | OEM-2-B | SPEEDUINO-A-16 | 0.5 | no route | Cooling fan relay | — | |
| W19 | OEM-2-C | SPEEDUINO-A-15 | 0.5 | no route | Condenser fan relay | — | |
| W20 | OEM-2-K | SPEEDUINO-A-36 | 0.5 | no route | A/C clutch relay | — | |
| W21 | OEM-2-M | SPEEDUINO-A-35 | 0.5 | no route | Fuel pump relay | — | |
| W22 | OEM-3-H | SPEEDUINO-A-37 | 0.5 | no route | Main relay | — | |
| W23 | OEM-3-J | SPEEDUINO-A-38 | 0.5 | no route | Front O2 heater | — | |
| W24 | OEM-3-P | SPEEDUINO-A-31 | 0.5 | no route | Rear O2 heater | — | |
| W25 | OEM-2-Q | SPEEDUINO-A-32 | 0.5 | no route | ISC valve low side | — | |
| W26 | OEM-2-E | SPEEDUINO-A-29 | 0.5 | no route | EGR valve | — | |
| W27 | OEM-2-F | SPEEDUINO-A-30 | 0.5 | no route | EGR valve | — | |
| W28 | OEM-3-O | SPEEDUINO-A-17 | 0.5 | no route | Tachometer output | — | |
| W29 | OEM-4-AE | SPEEDUINO-A-11 | 0.5 | no route | Pressure sensor (Mazda: EGR boost sensor) | — | |
| W30 | OEM-4-V | SPEEDUINO-A-22 | 0.5 | no route | Throttle position (TPS) | — | |
| W31 | OEM-4-AA | SPEEDUINO-A-21 | 0.5 | no route | Rear O2 signal | — | |
| W32 | OEM-4-P | SPEEDUINO-A-19 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W33 | OEM-4-N | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W34 | OEM-3-T | SPEEDUINO-A-14 | 0.5 | no route | Vehicle speed | — | |
| W35 | OEM-3-S | SPEEDUINO-A-18 | 0.5 | no route | Immobiliser | — |
Bill of materials
| Category | Part number | Manufacturer | Description | Qty | Unit |
|---|
ECU setup sheet
| Role | Engine ref | Engine signal | Sensor | ECU point | ECU function | ECU class | Setup flag |
|---|---|---|---|---|---|---|---|
| No configured channels. | |||||||
Findings
Open (13)
| Severity | Code | Subject | Message |
|---|---|---|---|
| error | REQUIRED_UNMAPPED | OEM-4-AF | Required OEM function "ECU power +14V (main relay)" (power_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-4-X | Required OEM function "Mass air flow (MAF)" (analog_in) is not connected to the new ECU. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-15 | SPEEDUINO-A-15 "Proto area 2 (fan)" drives OEM-2-C Condenser fan relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-16 | SPEEDUINO-A-16 "Proto area 3 (fuel pump)" drives OEM-2-B Cooling fan relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-32 | SPEEDUINO-A-32 "Idle stepper 1B" drives OEM-2-Q ISC valve low side (load 1.0 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-35 | SPEEDUINO-A-35 "Boost" drives OEM-2-M Fuel pump relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-36 | SPEEDUINO-A-36 "Idle 2 (3-wire idle)" drives OEM-2-K A/C clutch relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-37 | SPEEDUINO-A-37 "PWM idle" drives OEM-3-H Main relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | NET_FAMILY | OEM-2-E ↔ SPEEDUINO-A-29 | OEM-2-E "EGR valve" [low_side_out] is wired to SPEEDUINO-A-29 "Idle stepper 2B" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-2-F ↔ SPEEDUINO-A-30 | OEM-2-F "EGR valve" [low_side_out] is wired to SPEEDUINO-A-30 "Idle stepper 2A" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-2-Q ↔ SPEEDUINO-A-32 | OEM-2-Q "ISC valve low side" [low_side_out] is wired to SPEEDUINO-A-32 "Idle stepper 1B" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-3-P ↔ SPEEDUINO-A-31 | OEM-3-P "Rear O2 heater" [low_side_out] is wired to SPEEDUINO-A-31 "Idle stepper 1A" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| info | UNMAPPED | OEM | 19 optional OEM pins are not mapped: OEM-2-H EGR valve; OEM-2-I EGR valve; OEM-2-N VTCS solenoid (intake butterflies); OEM-2-P ISC valve +14V feed; OEM-2-R Malfunction indicator lamp (MIL); OEM-3-D EGR boost solenoid; OEM-3-E Charcoal canister purge; OEM-3-M Alternator control; OEM-3-U Charge lamp; OEM-4-AD Fuel level; OEM-4-B Brake switch; OEM-4-C Power steering pressure switch; OEM-4-D VVT oil-control solenoid; OEM-4-F A/C request; OEM-4-H Neutral switch; OEM-4-I Clutch switch; OEM-4-J VTCS vacuum switch; OEM-4-M Knock sensor; OEM-4-W Front O2 signal |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-4-AG | Battery-constant (memory) feed of the stock ECU: the new ECU has no such input, so it is not needed. | mapping-proposal |
Notes
Auto-mapped by auto_map() from the library pin data on 2026-10-09. Review every wire against both manuals before building. Open items: - Main-relay feed: no ecu_main_power pin on the stock or the new ECU - OEM-4 X: Mass air flow (MAF): no free maf/analog_0_5 on Speeduino Speeduino - OEM-4 AF: ECU power +14V (main relay): no rule for class ecu_main_power; wire by hand Not wired: - OEM-4 AG: Constant +12V: Speeduino Speeduino has no battery-constant input; not needed - OEM-4 M: Knock sensor: no free knock input on Speeduino Speeduino - OEM-2 H: EGR valve: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-2 I: EGR valve: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-2 N: VTCS solenoid (intake butterflies): no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-2 R: Malfunction indicator lamp (MIL): no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 E: Charcoal canister purge: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 M: Alternator control: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 U: Charge lamp: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-4 D: VVT oil-control solenoid: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-4 W: Front O2 signal: no free o2_narrowband/analog_0_5 on Speeduino Speeduino - OEM-4 AD: Fuel level: no free analog_0_5 on Speeduino Speeduino - OEM-4 B: Brake switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-4 C: Power steering pressure switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-4 F: A/C request: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-4 H: Neutral switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-4 I: Clutch switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-4 J: VTCS vacuum switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-2 P: ISC valve +14V feed: no rule for class switched_feed; wire by hand - OEM-3 D: EGR boost solenoid: not classified in the library; wire by hand
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | vendor_doc | Link G4X MX5NB2X install manual (NB2 2001-05) | https://linkecu.com/documentation/MX5XNB2.pdf | archive | 2026-10-05 | 741efdd9f2c8 |
| 4 | oem_manual | Mazda MX-5 NB2 (2003) wiring diagram — engine / starting / charging | https://web.archive.org/web/20191104195207/http://mellens.net/mazda/mazda_miata_extra_manual/2003_wiring.pdf | — | 2026-10-05 | 5ee0777f12c1 |
| 4 | vendor_doc | Speeduino Manual (08/04/25) — V0.4 board IDC40 pinout & features | https://speeduino.com/Speeduino_manual.pdf | archive | 2026-10-05 | 21806bd29ef0 |
| 2 | expert_report | Justin Barrera — Miata NA/NB wiring corrections | — | — | — | — |