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 | 31 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-4-V | SPEEDUINO-A-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-4-P | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-2-B | SPEEDUINO-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-2-C | SPEEDUINO-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-2-K | SPEEDUINO-A-36 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-2-M | SPEEDUINO-A-35 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-3-H | SPEEDUINO-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-2-O | SPEEDUINO-A-38 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-3-O | SPEEDUINO-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-4-AE | SPEEDUINO-A-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-4-AA | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-4-N | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-3-T | SPEEDUINO-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | 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 | — | W20 | — | 0.5 | SPEEDUINO-A-16 | — | — | — |
| C | Condenser fan relay | — | W21 | — | 0.5 | SPEEDUINO-A-15 | — | — | — |
| D | Injector 2 | — | W15 | — | 0.5 | SPEEDUINO-A-2 | — | — | — |
| E | EGR valve | — | — | — | — | — | — | — | — |
| F | EGR valve | — | — | — | — | — | — | — | — |
| 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 | — | W22 | — | 0.5 | SPEEDUINO-A-36 | — | — | — |
| L | NC | — | — | — | — | — | — | — | — |
| M | Fuel pump relay | — | W23 | — | 0.5 | SPEEDUINO-A-35 | — | — | — |
| N | VTCS solenoid (intake butterflies) | — | — | — | — | — | — | — | — |
| O | Fuel pump relay (non-immobiliser) | — | W25 | — | 0.5 | SPEEDUINO-A-38 | — | — | — |
| P | ISC valve +14V feed | — | — | — | — | — | — | — | — |
| Q | ISC valve low side | — | — | — | — | — | — | — | — |
| 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 | — | — | — |
| C | Purge solenoid valve | — | — | — | — | — | — | — | — |
| D | EGR boost solenoid | — | — | — | — | — | — | — | — |
| E | NC | — | — | — | — | — | — | — | — |
| F | Ignition 1 (coils 1+4, wasted spark) | — | W12 | — | 0.5 | SPEEDUINO-A-7 | — | — | — |
| G | NC | — | — | — | — | — | — | — | — |
| H | Main relay | — | W24 | — | 0.5 | SPEEDUINO-A-37 | — | — | — |
| I | Ignition 2 (coils 2+3, wasted spark) | — | W13 | — | 0.5 | SPEEDUINO-A-34 | — | — | — |
| J | Front O2 heater | — | — | — | — | — | — | — | — |
| K | EVAP leak detection pump | — | — | — | — | — | — | — | — |
| L | NC | — | — | — | — | — | — | — | — |
| M | Alternator control | — | — | — | — | — | — | — | — |
| N | NC | — | — | — | — | — | — | — | — |
| O | Tachometer output | — | W26 | — | 0.5 | SPEEDUINO-A-17 | — | — | — |
| P | Rear O2 heater | — | — | — | — | — | — | — | — |
| Q | Data link connector (K-line) | — | — | — | — | — | — | — | — |
| R | NC | — | — | — | — | — | — | — | — |
| S | Immobiliser | — | W31 | — | 0.5 | SPEEDUINO-A-18 | — | — | — |
| T | Vehicle speed | — | W30 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| U | Charge lamp | — | — | — | — | — | — | — | — |
| V | Cam position (CMP) | — | W11 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| W | NC | — | — | — | — | — | — | — | — |
| X | NC | — | — | — | — | — | — | — | — |
| Y | Crank position (CKP) | — | W10 | — | 0.5 | SPEEDUINO-A-25 | — | — | — |
| Z | NC | — | — | — | — | — | — | — | — |
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 | — | W28 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| AB | NC | — | — | — | — | — | — | — | — |
| AC | TCM (automatic only) | — | — | — | — | — | — | — | — |
| AD | Fuel level | — | — | — | — | — | — | — | — |
| AE | Pressure sensor (Mazda: EGR boost sensor) | — | W27 | — | 0.5 | SPEEDUINO-A-11 | — | — | — |
| AF | ECU power +14V (main relay) | — | — | — | — | — | — | — | — |
| AG | Constant +12V | — | — | — | — | — | — | — | — |
| AH | EVAP leak detection pump solenoid valve | — | — | — | — | — | — | — | — |
| B | Brake switch | — | — | — | — | — | — | — | — |
| C | Power steering pressure switch | — | — | — | — | — | — | — | — |
| D | VVT oil-control solenoid +12V feed | — | — | — | — | — | — | — | — |
| E | Diagnostic (DLC TEN) (NA) | — | — | — | — | — | — | — | — |
| F | A/C request | — | — | — | — | — | — | — | — |
| G | NC | — | — | — | — | — | — | — | — |
| H | Neutral switch | — | — | — | — | — | — | — | — |
| I | Clutch switch | — | — | — | — | — | — | — | — |
| J | VTCS vacuum switch | — | — | — | — | — | — | — | — |
| K | NC | — | — | — | — | — | — | — | — |
| L | +5V sensor supply | — | W9 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
| M | Knock sensor | — | — | — | — | — | — | — | — |
| N | Intake air temperature (IAT) | — | W29 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
| O | Signal ground | — | W6 | — | 0.5 | SP-0V-1 | — | — | — |
| P | Coolant temperature (ECT) | — | W19 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| Q | NC | — | — | — | — | — | — | — | — |
| R | VVT oil-control solenoid (low-side control) | — | — | — | — | — | — | — | — |
| S | Ignition switch (IG1) sense | — | — | — | — | — | — | — | — |
| T | Generator output voltage (terminal P) | — | — | — | — | — | — | — | — |
| U | NC | — | — | — | — | — | — | — | — |
| V | Throttle position (TPS) | — | W18 | — | 0.5 | SPEEDUINO-A-22 | — | — | — |
| W | Front O2 signal | — | — | — | — | — | — | — | — |
| X | Mass air flow (MAF) | — | — | — | — | — | — | — | — |
| Y | NC | — | — | — | — | — | — | — | — |
| Z | TCM (automatic only) | — | — | — | — | — | — | — | — |
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) | — | W27 | — | 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) | — | W30 | — | 0.5 | OEM-3-T | — | — | — |
| 15 | Proto area 2 (fan) | — | W21 | — | 0.5 | OEM-2-C | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | W20 | — | 0.5 | OEM-2-B | — | — | — |
| 17 | Proto area 4 (tachometer) | — | W26 | — | 0.5 | OEM-3-O | — | — | — |
| 18 | Proto area 5 (clutch) | — | W31 | — | 0.5 | OEM-3-S | — | — | — |
| 19 | Coolant temp (CLT) | — | W19 | — | 0.5 | OEM-4-P | — | — | — |
| 2 | Injector 2 | — | W15 | — | 0.5 | OEM-2-D | — | — | — |
| 20 | Inlet air temp (IAT) | — | W29 | — | 0.5 | OEM-4-N | — | — | — |
| 21 | O2 sensor | — | W28 | — | 0.5 | OEM-4-AA | — | — | — |
| 22 | TPS input | — | W18 | — | 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 | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | W16 | — | 0.5 | OEM-2-G | — | — | — |
| 30 | Idle stepper 2A | — | — | — | — | — | — | — | — |
| 31 | Idle stepper 1A | — | — | — | — | — | — | — | — |
| 32 | Idle stepper 1B | — | — | — | — | — | — | — | — |
| 33 | Ignition 3 | — | — | — | — | — | — | — | — |
| 34 | Ignition 2 | — | W13 | — | 0.5 | OEM-3-I | — | — | — |
| 35 | Boost | — | W23 | — | 0.5 | OEM-2-M | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | W22 | — | 0.5 | OEM-2-K | — | — | — |
| 37 | PWM idle | — | W24 | — | 0.5 | OEM-3-H | — | — | — |
| 38 | VVT | — | W25 | — | 0.5 | OEM-2-O | — | — | — |
| 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 | YB | single_source |
| OEM-2-B | Cooling fan relay | low_side_out | SPEEDUINO-A-16 | Proto area 3 (fuel pump) | low_side_out | RY | single_source |
| OEM-2-C | Condenser fan relay | low_side_out | SPEEDUINO-A-15 | Proto area 2 (fan) | low_side_out | LW | single_source |
| OEM-2-D | Injector 2 | injector_out | SPEEDUINO-A-2 | Injector 2 | injector_out | VG | single_source |
| OEM-2-E | EGR valve | low_side_out | — | — | — | Lg | single_source |
| OEM-2-F | EGR valve | low_side_out | — | — | — | WG | single_source |
| OEM-2-G | Injector 3 | injector_out | SPEEDUINO-A-3 | Injector 3 | injector_out | YR | single_source |
| OEM-2-H | EGR valve | low_side_out | — | — | — | PB | single_source |
| OEM-2-I | EGR valve | low_side_out | — | — | — | P | single_source |
| OEM-2-J | Injector 4 | injector_out | SPEEDUINO-A-5 | Injector 4 | injector_out | YG | single_source |
| OEM-2-K | A/C clutch relay | low_side_out | SPEEDUINO-A-36 | Idle 2 (3-wire idle) | low_side_out | LB | single_source |
| OEM-2-L | NC | — | — | — | — | unverified | |
| OEM-2-M | Fuel pump relay | low_side_out | SPEEDUINO-A-35 | Boost | low_side_out | RW | single_source |
| OEM-2-N | VTCS solenoid (intake butterflies) | low_side_out | — | — | — | BW | single_source |
| OEM-2-O | Fuel pump relay (non-immobiliser) | low_side_out | SPEEDUINO-A-38 | VVT | low_side_out | R | single_source |
| OEM-2-P | ISC valve +14V feed | power_in | — | — | — | Or | single_source |
| OEM-2-Q | ISC valve low side | low_side_out | — | — | — | VR | single_source |
| OEM-2-R | Malfunction indicator lamp (MIL) | low_side_out | — | — | — | WL | single_source |
| OEM-3-A | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | B | single_source |
| OEM-3-B | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | BR | single_source |
| OEM-3-C | Purge solenoid valve | low_side_out | — | — | — | GY | single_source |
| OEM-3-D | EGR boost solenoid | — | — | — | — | GyB | single_source |
| OEM-3-E | NC | — | — | — | — | unverified | |
| OEM-3-F | Ignition 1 (coils 1+4, wasted spark) | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | BrW | single_source |
| OEM-3-G | NC | — | — | — | — | unverified | |
| OEM-3-H | Main relay | low_side_out | SPEEDUINO-A-37 | PWM idle | low_side_out | LOr | single_source |
| OEM-3-I | Ignition 2 (coils 2+3, wasted spark) | ignition_out | SPEEDUINO-A-34 | Ignition 2 | ignition_out | BY | single_source |
| OEM-3-J | Front O2 heater | low_side_out | — | — | — | BOr | single_source |
| OEM-3-K | EVAP leak detection pump | low_side_out | — | — | — | YB | single_source |
| OEM-3-L | NC | — | — | — | — | unverified | |
| OEM-3-M | Alternator control | low_side_out | — | — | — | GyR | single_source |
| OEM-3-N | NC | — | — | — | — | unverified | |
| OEM-3-O | Tachometer output | tacho_out | SPEEDUINO-A-17 | Proto area 4 (tachometer) | tacho_out | GOr | single_source |
| OEM-3-P | Rear O2 heater | low_side_out | — | — | — | WB | single_source |
| OEM-3-Q | Data link connector (K-line) | serial | — | — | — | GW | single_source |
| OEM-3-R | NC | — | — | — | — | unverified | |
| OEM-3-S | Immobiliser | digital_in | SPEEDUINO-A-18 | Proto area 5 (clutch) | digital_in | RB | single_source |
| OEM-3-T | Vehicle speed | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | GR | single_source |
| OEM-3-U | Charge lamp | low_side_out | — | — | — | BrR | single_source |
| OEM-3-V | Cam position (CMP) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | GyL | single_source |
| OEM-3-W | NC | — | — | — | — | unverified | |
| OEM-3-X | NC | — | — | — | — | unverified | |
| OEM-3-Y | Crank position (CKP) | trigger_in | SPEEDUINO-A-25 | Crank input / VR1+ | trigger_in | VW | single_source |
| OEM-3-Z | NC | — | — | — | — | unverified | |
| OEM-4-A | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | BL | single_source |
| OEM-4-AA | Rear O2 signal | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | R | single_source |
| OEM-4-AB | NC | — | — | — | — | unverified | |
| OEM-4-AC | TCM (automatic only) | — | — | — | — | VG | single_source |
| OEM-4-AD | Fuel level | analog_in | — | — | — | BrB | single_source |
| OEM-4-AE | Pressure sensor (Mazda: EGR boost sensor) | analog_in | SPEEDUINO-A-11 | MAP sensor (0-5V) | analog_in | LY | corroborated |
| OEM-4-AF | ECU power +14V (main relay) | power_in | — | — | — | WR | single_source |
| OEM-4-AG | Constant +12V | power_in | — | — | — | LR | single_source |
| OEM-4-AH | EVAP leak detection pump solenoid valve | low_side_out | — | — | — | RG | single_source |
| OEM-4-B | Brake switch | digital_in | — | — | — | G | single_source |
| OEM-4-C | Power steering pressure switch | digital_in | — | — | — | Br | single_source |
| OEM-4-D | VVT oil-control solenoid +12V feed | power_in | — | — | — | Y | single_source |
| OEM-4-E | Diagnostic (DLC TEN) (NA) | serial | — | — | — | LY | single_source |
| OEM-4-F | A/C request | digital_in | — | — | — | LgB | single_source |
| OEM-4-G | NC | — | — | — | — | unverified | |
| OEM-4-H | Neutral switch | digital_in | — | — | — | V | single_source |
| OEM-4-I | Clutch switch | digital_in | — | — | — | WG | single_source |
| OEM-4-J | VTCS vacuum switch | digital_in | — | — | — | Or | single_source |
| OEM-4-K | NC | — | — | — | — | unverified | |
| OEM-4-L | +5V sensor supply | vref | SPEEDUINO-A-13 | 5V | vref | LgR | single_source |
| OEM-4-M | Knock sensor | knock_in | — | — | — | W | single_source |
| OEM-4-N | Intake air temperature (IAT) | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | PL | single_source |
| OEM-4-O | Signal ground | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | BR | single_source |
| OEM-4-P | Coolant temperature (ECT) | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | RL | single_source |
| OEM-4-Q | NC | — | — | — | — | unverified | |
| OEM-4-R | VVT oil-control solenoid (low-side control) | low_side_out | — | — | — | VY | corroborated |
| OEM-4-S | Ignition switch (IG1) sense | digital_in | — | — | — | BW | single_source |
| OEM-4-T | Generator output voltage (terminal P) | — | — | — | — | Gy | single_source |
| OEM-4-U | NC | — | — | — | — | unverified | |
| OEM-4-V | Throttle position (TPS) | analog_in | SPEEDUINO-A-22 | TPS input | analog_in | GB | single_source |
| OEM-4-W | Front O2 signal | lambda_nb_in | — | — | — | L | single_source |
| OEM-4-X | Mass air flow (MAF) | analog_in | — | — | — | P | single_source |
| OEM-4-Y | NC | — | — | — | — | unverified | |
| OEM-4-Z | TCM (automatic only) | — | — | — | — | PB | 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-4-V | SPEEDUINO-A-22 | 0.5 | no route | Throttle position (TPS) | — | |
| W19 | OEM-4-P | SPEEDUINO-A-19 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W20 | OEM-2-B | SPEEDUINO-A-16 | 0.5 | no route | Cooling fan relay | — | |
| W21 | OEM-2-C | SPEEDUINO-A-15 | 0.5 | no route | Condenser fan relay | — | |
| W22 | OEM-2-K | SPEEDUINO-A-36 | 0.5 | no route | A/C clutch relay | — | |
| W23 | OEM-2-M | SPEEDUINO-A-35 | 0.5 | no route | Fuel pump relay | — | |
| W24 | OEM-3-H | SPEEDUINO-A-37 | 0.5 | no route | Main relay | — | |
| W25 | OEM-2-O | SPEEDUINO-A-38 | 0.5 | no route | Fuel pump relay (non-immobiliser) | — | |
| W26 | OEM-3-O | SPEEDUINO-A-17 | 0.5 | no route | Tachometer output | — | |
| W27 | OEM-4-AE | SPEEDUINO-A-11 | 0.5 | no route | Pressure sensor (Mazda: EGR boost sensor) | — | |
| W28 | OEM-4-AA | SPEEDUINO-A-21 | 0.5 | no route | Rear O2 signal | — | |
| W29 | OEM-4-N | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W30 | OEM-3-T | SPEEDUINO-A-14 | 0.5 | no route | Vehicle speed | — | |
| W31 | 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 (8)
| 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-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. |
| info | UNMAPPED | OEM | 33 optional OEM pins are not mapped: OEM-2-E EGR valve; OEM-2-F EGR valve; 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-Q ISC valve low side; OEM-2-R Malfunction indicator lamp (MIL); OEM-3-C Purge solenoid valve; OEM-3-D EGR boost solenoid; OEM-3-J Front O2 heater; OEM-3-K EVAP leak detection pump; OEM-3-M Alternator control; OEM-3-P Rear O2 heater; OEM-3-Q Data link connector (K-line); OEM-3-U Charge lamp; OEM-4-AC TCM (automatic only); OEM-4-AD Fuel level; OEM-4-AH EVAP leak detection pump solenoid valve; OEM-4-B Brake switch; OEM-4-C Power steering pressure switch; OEM-4-D VVT oil-control solenoid +12V feed; OEM-4-E Diagnostic (DLC TEN) (NA); 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-R VVT oil-control solenoid (low-side control); OEM-4-S Ignition switch (IG1) sense; OEM-4-T Generator output voltage (terminal P); OEM-4-W Front O2 signal; OEM-4-Z TCM (automatic only) |
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 2026-10-11. 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-4 S: Ignition switch (IG1) sense: key-on 12 V sense — optional in a swap (the main relay is energized from keyed 12 V, not from this pin); Speeduino Speeduino has no dedicated key-on input - OEM-3 J: Front O2 heater: no free heater_low_side/low_side/relay_control/ls_hs/injector on Speeduino Speeduino - OEM-3 P: Rear O2 heater: no free heater_low_side/low_side/relay_control/ls_hs/injector on Speeduino Speeduino - OEM-2 Q: ISC valve low side: no free low_side/relay_control/heater_low_side/ls_hs/injector rated ≥ 1.0 A on Speeduino Speeduino - OEM-2 E: EGR valve: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 F: EGR valve: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 H: EGR valve: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 I: EGR valve: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 N: VTCS solenoid (intake butterflies): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 R: Malfunction indicator lamp (MIL): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-3 C: Purge solenoid valve: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-3 K: EVAP leak detection pump: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-3 M: Alternator control: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-3 U: Charge lamp: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-4 AH: EVAP leak detection pump solenoid valve: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-4 R: VVT oil-control solenoid (low-side control): no free low_side/relay_control/heater_low_side/ls_hs/injector 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-3 Q: Data link connector (K-line): no free k_line on Speeduino Speeduino - OEM-4 E: Diagnostic (DLC TEN) (NA): no free k_line on Speeduino Speeduino - OEM-4 D: VVT oil-control solenoid +12V feed: no rule for class switched_feed; wire by hand - 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 - OEM-4 AC: TCM (automatic only): not classified in the library; wire by hand - OEM-4 T: Generator output voltage (terminal P): not classified in the library; wire by hand - OEM-4 Z: TCM (automatic only): not classified in the library; wire by hand
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | oem_manual | 2005 Mazda MX-5 Miata Engine Performance Control System (PCM terminal voltage reference, BP and BP WITH TC) | https://trull.org/alex/pubmirror/www.mellens.net/mazda/Mazda-Miata-2005/engine_control_system.pdf | — | — | — |
| 4 | vendor_doc | Adaptronic eSel039 Select Plugin ECU for Mazda MX5 / Miata NB8B/C (OEM ECU pinout) | https://www.miataturbo.net/attachments/ecus-tuning-54/04-msm-ecu-pinout-104032/nb8bc_oem_ecu_pinouts-224948d1602912806 | — | — | — |
| 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 | — | — | — | — |