MX-5 Miata NB1 1999-00 (BP-4W) → 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 3S) 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 (2000 FSM P0107/P0108). 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 3S).
Source: 2000 Mazda MX-5 Miata factory service manual — engine self-diagnostics (DTC P0106/P0107/P0108)
| 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 · 3 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-3-C | 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-3-F | 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-2-I | SPEEDUINO-A-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-2-J | SPEEDUINO-A-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-2-H | SPEEDUINO-A-24 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | OEM-3-G | SPEEDUINO-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-3-H | SPEEDUINO-A-34 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-3-W | SPEEDUINO-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-3-X | SPEEDUINO-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-3-Y | SPEEDUINO-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-3-Z | SPEEDUINO-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-1-I | SPEEDUINO-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-1-R | SPEEDUINO-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-1-S | SPEEDUINO-A-36 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-3-N | SPEEDUINO-A-35 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-1-U | SPEEDUINO-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-3-V | SPEEDUINO-A-38 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-3-O | SPEEDUINO-A-31 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-1-E | SPEEDUINO-A-32 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-1-O | SPEEDUINO-A-29 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-1-Q | SPEEDUINO-A-30 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-2-K | SPEEDUINO-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-3-S | SPEEDUINO-A-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-3-E | SPEEDUINO-A-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-2-C | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-2-E | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-2-B | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-2-D | SPEEDUINO-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-1-F | 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-10 | open (OL) | 5 V sensor reference must not touch power ground | |
| 2 | SPEEDUINO-A-13 | SPEEDUINO-A-12 | open (OL) | 5 V sensor reference must not touch sensor ground |
If any reading doesn't match, stop and get help before powering up.
Revisions
| Rev | Label | By | Date |
|---|---|---|---|
| No revisions yet. | |||
Schematic
Connectors
OEM-1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Constant +12V | — | — | — | — | — | — | — | — |
| B | ECU power +14V (main relay) | — | — | — | — | — | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | W25 | — | 0.5 | SPEEDUINO-A-32 | — | — | — |
| F | Brake switch | — | W35 | — | 0.5 | SPEEDUINO-A-18 | — | — | — |
| G | Power steering pressure switch | — | — | — | — | — | — | — | — |
| I | Condenser fan relay | — | W18 | — | 0.5 | SPEEDUINO-A-16 | — | — | — |
| O | Alternator control | — | W26 | — | 0.5 | SPEEDUINO-A-29 | — | — | — |
| P | A/C request | — | — | — | — | — | — | — | — |
| Q | Charge lamp | — | W27 | — | 0.5 | SPEEDUINO-A-30 | — | — | — |
| R | Cooling fan relay | — | W19 | — | 0.5 | SPEEDUINO-A-15 | — | — | — |
| S | A/C clutch relay | — | W20 | — | 0.5 | SPEEDUINO-A-36 | — | — | — |
| U | Front O2 heater | — | W22 | — | 0.5 | SPEEDUINO-A-37 | — | — | — |
| V | Neutral switch | — | — | — | — | — | — | — | — |
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Fuel tank pressure | — | — | — | — | — | — | — | — |
| B | Intake air temperature (IAT) | — | W33 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
| C | Front O2 signal | — | W31 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| D | Vehicle speed | — | W34 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| E | Coolant temperature (ECT) | — | W32 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| F | Knock sensor | — | — | — | — | — | — | — | — |
| H | Cam position (CMP) | — | W11 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| I | +5V sensor supply | — | W9 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
| J | Crank position (CKP) | — | W10 | — | 0.5 | SPEEDUINO-A-25 | — | — | — |
| K | Tachometer output | — | W28 | — | 0.5 | SPEEDUINO-A-17 | — | — | — |
| L | Mass air flow (MAF) | — | — | — | — | — | — | — | — |
| M | EGR valve | — | — | — | — | — | — | — | — |
| N | EGR valve | — | — | — | — | — | — | — | — |
| O | EGR valve | — | — | — | — | — | — | — | — |
| P | EGR valve | — | — | — | — | — | — | — | — |
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 | Power ground | — | W3 | — | 0.85 | SP-GND-1 | — | — | — |
| E | Throttle position (TPS) | — | W30 | — | 0.5 | SPEEDUINO-A-22 | — | — | — |
| F | Signal ground | — | W6 | — | 0.5 | SP-0V-1 | — | — | — |
| G | Ignition 1 (coils 1+4, wasted spark) | — | W12 | — | 0.5 | SPEEDUINO-A-7 | — | — | — |
| H | Ignition 2 (coils 2+3, wasted spark) | — | W13 | — | 0.5 | SPEEDUINO-A-34 | — | — | — |
| I | Clutch switch | — | — | — | — | — | — | — | — |
| J | Rear O2 signal | — | — | — | — | — | — | — | — |
| K | Fuel level | — | — | — | — | — | — | — | — |
| L | Evap purge solenoid | — | — | — | — | — | — | — | — |
| M | ISC valve +14V feed | — | — | — | — | — | — | — | — |
| N | Fuel pump relay | — | W21 | — | 0.5 | SPEEDUINO-A-35 | — | — | — |
| O | ISC valve low side | — | W24 | — | 0.5 | SPEEDUINO-A-31 | — | — | — |
| Q | VICS solenoid (intake butterflies) | — | — | — | — | — | — | — | — |
| S | Pressure sensor (Mazda: EGR boost sensor) | — | W29 | — | 0.5 | SPEEDUINO-A-11 | — | — | — |
| T | EGR boost solenoid | — | — | — | — | — | — | — | — |
| U | Canister drain cut valve (CDCV) | — | — | — | — | — | — | — | — |
| V | Rear O2 heater | — | W23 | — | 0.5 | SPEEDUINO-A-38 | — | — | — |
| W | Injector 1 | — | W14 | — | 0.5 | SPEEDUINO-A-1 | — | — | — |
| X | Injector 2 | — | W15 | — | 0.5 | SPEEDUINO-A-2 | — | — | — |
| Y | Injector 3 | — | W16 | — | 0.5 | SPEEDUINO-A-3 | — | — | — |
| Z | Injector 4 | — | W17 | — | 0.5 | SPEEDUINO-A-5 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W6 | — | 0.5 | OEM-3-F | — | — | — |
| 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-3-C | — | — | — |
| 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-3-W | — | — | — |
| 10 | Ground | — | W4 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | MAP sensor (0-5V) | — | W29 | — | 0.5 | OEM-3-S | — | — | — |
| 12 | Ground | — | W7 | — | 0.5 | SP-0V-1 | — | — | — |
| 13 | 5V | — | W9 | — | 0.5 | OEM-2-I | — | — | — |
| 14 | Proto area 1 (flex fuel) | — | W34 | — | 0.5 | OEM-2-D | — | — | — |
| 15 | Proto area 2 (fan) | — | W19 | — | 0.5 | OEM-1-R | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | W18 | — | 0.5 | OEM-1-I | — | — | — |
| 17 | Proto area 4 (tachometer) | — | W28 | — | 0.5 | OEM-2-K | — | — | — |
| 18 | Proto area 5 (clutch) | — | W35 | — | 0.5 | OEM-1-F | — | — | — |
| 19 | Coolant temp (CLT) | — | W32 | — | 0.5 | OEM-2-E | — | — | — |
| 2 | Injector 2 | — | W15 | — | 0.5 | OEM-3-X | — | — | — |
| 20 | Inlet air temp (IAT) | — | W33 | — | 0.5 | OEM-2-B | — | — | — |
| 21 | O2 sensor | — | W31 | — | 0.5 | OEM-2-C | — | — | — |
| 22 | TPS input | — | W30 | — | 0.5 | OEM-3-E | — | — | — |
| 23 | Ground | — | W8 | — | 0.5 | SP-0V-1 | — | — | — |
| 24 | Cam input / VR2+ | — | W11 | — | 0.5 | OEM-2-H | — | — | — |
| 25 | Crank input / VR1+ | — | W10 | — | 0.5 | OEM-2-J | — | — | — |
| 26 | VR2- | — | — | — | — | — | — | — | — |
| 27 | VR1- | — | — | — | — | — | — | — | — |
| 28 | 5V | — | — | — | — | — | — | — | — |
| 29 | Idle stepper 2B | — | W26 | — | 0.5 | OEM-1-O | — | — | — |
| 3 | Injector 3 | — | W16 | — | 0.5 | OEM-3-Y | — | — | — |
| 30 | Idle stepper 2A | — | W27 | — | 0.5 | OEM-1-Q | — | — | — |
| 31 | Idle stepper 1A | — | W24 | — | 0.5 | OEM-3-O | — | — | — |
| 32 | Idle stepper 1B | — | W25 | — | 0.5 | OEM-1-E | — | — | — |
| 33 | Ignition 3 | — | — | — | — | — | — | — | — |
| 34 | Ignition 2 | — | W13 | — | 0.5 | OEM-3-H | — | — | — |
| 35 | Boost | — | W21 | — | 0.5 | OEM-3-N | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | W20 | — | 0.5 | OEM-1-S | — | — | — |
| 37 | PWM idle | — | W22 | — | 0.5 | OEM-1-U | — | — | — |
| 38 | VVT | — | W23 | — | 0.5 | OEM-3-V | — | — | — |
| 5 | Injector 4 | — | W17 | — | 0.5 | OEM-3-Z | — | — | — |
| 7 | Ignition 1 | — | W12 | — | 0.5 | OEM-3-G | — | — | — |
| 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-1-A | Constant +12V | power_in | — | — | — | single_source | |
| OEM-1-B | ECU power +14V (main relay) | power_in | — | — | — | single_source | |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | SPEEDUINO-A-32 | Idle stepper 1B | hbridge_out | single_source | |
| OEM-1-F | Brake switch | digital_in | SPEEDUINO-A-18 | Proto area 5 (clutch) | digital_in | single_source | |
| OEM-1-G | Power steering pressure switch | digital_in | — | — | — | single_source | |
| OEM-1-I | Condenser fan relay | low_side_out | SPEEDUINO-A-16 | Proto area 3 (fuel pump) | low_side_out | single_source | |
| OEM-1-O | Alternator control | low_side_out | SPEEDUINO-A-29 | Idle stepper 2B | hbridge_out | single_source | |
| OEM-1-P | A/C request | digital_in | — | — | — | single_source | |
| OEM-1-Q | Charge lamp | low_side_out | SPEEDUINO-A-30 | Idle stepper 2A | hbridge_out | single_source | |
| OEM-1-R | Cooling fan relay | low_side_out | SPEEDUINO-A-15 | Proto area 2 (fan) | low_side_out | single_source | |
| OEM-1-S | A/C clutch relay | low_side_out | SPEEDUINO-A-36 | Idle 2 (3-wire idle) | low_side_out | single_source | |
| OEM-1-U | Front O2 heater | low_side_out | SPEEDUINO-A-37 | PWM idle | low_side_out | single_source | |
| OEM-1-V | Neutral switch | digital_in | — | — | — | single_source | |
| OEM-2-A | Fuel tank pressure | analog_in | — | — | — | single_source | |
| OEM-2-B | Intake air temperature (IAT) | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | single_source | |
| OEM-2-C | Front O2 signal | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | single_source | |
| OEM-2-D | Vehicle speed | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | single_source | |
| OEM-2-E | Coolant temperature (ECT) | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | single_source | |
| OEM-2-F | Knock sensor | knock_in | — | — | — | single_source | |
| OEM-2-H | Cam position (CMP) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | single_source | |
| OEM-2-I | +5V sensor supply | vref | SPEEDUINO-A-13 | 5V | vref | single_source | |
| OEM-2-J | Crank position (CKP) | trigger_in | SPEEDUINO-A-25 | Crank input / VR1+ | trigger_in | single_source | |
| OEM-2-K | Tachometer output | tacho_out | SPEEDUINO-A-17 | Proto area 4 (tachometer) | tacho_out | single_source | |
| OEM-2-L | Mass air flow (MAF) | analog_in | — | — | — | single_source | |
| OEM-2-M | EGR valve | low_side_out | — | — | — | single_source | |
| OEM-2-N | EGR valve | low_side_out | — | — | — | single_source | |
| OEM-2-O | EGR valve | low_side_out | — | — | — | single_source | |
| OEM-2-P | EGR valve | 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-C | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-3-E | Throttle position (TPS) | analog_in | SPEEDUINO-A-22 | TPS input | analog_in | single_source | |
| OEM-3-F | Signal ground | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | single_source | |
| OEM-3-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | single_source | |
| OEM-3-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | SPEEDUINO-A-34 | Ignition 2 | ignition_out | single_source | |
| OEM-3-I | Clutch switch | digital_in | — | — | — | single_source | |
| OEM-3-J | Rear O2 signal | lambda_nb_in | — | — | — | single_source | |
| OEM-3-K | Fuel level | analog_in | — | — | — | single_source | |
| OEM-3-L | Evap purge solenoid | low_side_out | — | — | — | single_source | |
| OEM-3-M | ISC valve +14V feed | power_in | — | — | — | single_source | |
| OEM-3-N | Fuel pump relay | low_side_out | SPEEDUINO-A-35 | Boost | low_side_out | single_source | |
| OEM-3-O | ISC valve low side | low_side_out | SPEEDUINO-A-31 | Idle stepper 1A | hbridge_out | single_source | |
| OEM-3-Q | VICS solenoid (intake butterflies) | low_side_out | — | — | — | single_source | |
| OEM-3-S | Pressure sensor (Mazda: EGR boost sensor) | analog_in | SPEEDUINO-A-11 | MAP sensor (0-5V) | analog_in | single_source | |
| OEM-3-T | EGR boost solenoid | — | — | — | — | single_source | |
| OEM-3-U | Canister drain cut valve (CDCV) | low_side_out | — | — | — | single_source | |
| OEM-3-V | Rear O2 heater | low_side_out | SPEEDUINO-A-38 | VVT | low_side_out | single_source | |
| OEM-3-W | Injector 1 | injector_out | SPEEDUINO-A-1 | Injector 1 | injector_out | single_source | |
| OEM-3-X | Injector 2 | injector_out | SPEEDUINO-A-2 | Injector 2 | injector_out | single_source | |
| OEM-3-Y | Injector 3 | injector_out | SPEEDUINO-A-3 | Injector 3 | injector_out | single_source | |
| OEM-3-Z | Injector 4 | injector_out | SPEEDUINO-A-5 | Injector 4 | injector_out | 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-3-C | 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-3-F | 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-2-I | SPEEDUINO-A-13 | 0.5 | no route | +5V sensor supply | — | |
| W10 | OEM-2-J | SPEEDUINO-A-25 | 0.5 | no route | Crank position (CKP) | — | |
| W11 | OEM-2-H | SPEEDUINO-A-24 | 0.5 | no route | Cam position (CMP) | — | |
| W12 | OEM-3-G | SPEEDUINO-A-7 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W13 | OEM-3-H | SPEEDUINO-A-34 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W14 | OEM-3-W | SPEEDUINO-A-1 | 0.5 | no route | Injector 1 | — | |
| W15 | OEM-3-X | SPEEDUINO-A-2 | 0.5 | no route | Injector 2 | — | |
| W16 | OEM-3-Y | SPEEDUINO-A-3 | 0.5 | no route | Injector 3 | — | |
| W17 | OEM-3-Z | SPEEDUINO-A-5 | 0.5 | no route | Injector 4 | — | |
| W18 | OEM-1-I | SPEEDUINO-A-16 | 0.5 | no route | Condenser fan relay | — | |
| W19 | OEM-1-R | SPEEDUINO-A-15 | 0.5 | no route | Cooling fan relay | — | |
| W20 | OEM-1-S | SPEEDUINO-A-36 | 0.5 | no route | A/C clutch relay | — | |
| W21 | OEM-3-N | SPEEDUINO-A-35 | 0.5 | no route | Fuel pump relay | — | |
| W22 | OEM-1-U | SPEEDUINO-A-37 | 0.5 | no route | Front O2 heater | — | |
| W23 | OEM-3-V | SPEEDUINO-A-38 | 0.5 | no route | Rear O2 heater | — | |
| W24 | OEM-3-O | SPEEDUINO-A-31 | 0.5 | no route | ISC valve low side | — | |
| W25 | OEM-1-E | SPEEDUINO-A-32 | 0.5 | no route | Malfunction indicator lamp (MIL) | — | |
| W26 | OEM-1-O | SPEEDUINO-A-29 | 0.5 | no route | Alternator control | — | |
| W27 | OEM-1-Q | SPEEDUINO-A-30 | 0.5 | no route | Charge lamp | — | |
| W28 | OEM-2-K | SPEEDUINO-A-17 | 0.5 | no route | Tachometer output | — | |
| W29 | OEM-3-S | SPEEDUINO-A-11 | 0.5 | no route | Pressure sensor (Mazda: EGR boost sensor) | — | |
| W30 | OEM-3-E | SPEEDUINO-A-22 | 0.5 | no route | Throttle position (TPS) | — | |
| W31 | OEM-2-C | SPEEDUINO-A-21 | 0.5 | no route | Front O2 signal | — | |
| W32 | OEM-2-E | SPEEDUINO-A-19 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W33 | OEM-2-B | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W34 | OEM-2-D | SPEEDUINO-A-14 | 0.5 | no route | Vehicle speed | — | |
| W35 | OEM-1-F | SPEEDUINO-A-18 | 0.5 | no route | Brake switch | — |
Bill of materials
| Category | Part number | Manufacturer | Description | Qty | Unit |
|---|---|---|---|---|---|
| connector | 174514-6 | TE | AMP Multilock .040/.070 hybrid 16-pin female harness plug (Miata NB1 ECU) | 1.000 | ea |
| connector | 174515-6 | TE | AMP Multilock .040/.070 hybrid 22-pin female harness plug (Miata NA/NB ECU) | 1.000 | ea |
| connector | 174516-6 | TE | AMP Multilock .040/.070 hybrid 26-pin female harness plug (Miata NA/NB ECU) | 1.000 | ea |
ECU setup sheet
| Role | Engine ref | Engine signal | Sensor | ECU point | ECU function | ECU class | Setup flag |
|---|---|---|---|---|---|---|---|
| No configured channels. | |||||||
Findings
Open (12)
| Severity | Code | Subject | Message |
|---|---|---|---|
| error | REQUIRED_UNMAPPED | OEM-1-B | Required OEM function "ECU power +14V (main relay)" (power_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-2-L | 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-1-R Cooling 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-1-I Condenser fan relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-31 | SPEEDUINO-A-31 "Idle stepper 1A" drives OEM-3-O 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-3-N 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-1-S A/C clutch relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | NET_FAMILY | OEM-1-E ↔ SPEEDUINO-A-32 | OEM-1-E "Malfunction indicator lamp (MIL)" [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-1-O ↔ SPEEDUINO-A-29 | OEM-1-O "Alternator control" [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-1-Q ↔ SPEEDUINO-A-30 | OEM-1-Q "Charge lamp" [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-3-O ↔ SPEEDUINO-A-31 | OEM-3-O "ISC valve low side" [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 | 17 optional OEM pins are not mapped: OEM-1-G Power steering pressure switch; OEM-1-P A/C request; OEM-1-V Neutral switch; OEM-2-A Fuel tank pressure; OEM-2-F Knock sensor; OEM-2-M EGR valve; OEM-2-N EGR valve; OEM-2-O EGR valve; OEM-2-P EGR valve; OEM-3-I Clutch switch; OEM-3-J Rear O2 signal; OEM-3-K Fuel level; OEM-3-L Evap purge solenoid; OEM-3-M ISC valve +14V feed; OEM-3-Q VICS solenoid (intake butterflies); OEM-3-T EGR boost solenoid; OEM-3-U Canister drain cut valve (CDCV) |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-1-A | 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-2 L: Mass air flow (MAF): no free maf/analog_0_5 on Speeduino Speeduino - OEM-1 B: ECU power +14V (main relay): no rule for class ecu_main_power; wire by hand Not wired: - OEM-1 A: Constant +12V: Speeduino Speeduino has no battery-constant input; not needed - OEM-2 F: Knock sensor: no free knock input on Speeduino Speeduino - OEM-2 M: EGR valve: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-2 N: EGR valve: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-2 O: EGR valve: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-2 P: EGR valve: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 L: Evap purge solenoid: no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 Q: VICS solenoid (intake butterflies): no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 U: Canister drain cut valve (CDCV): no free low_side/ls_hs/injector/hbridge on Speeduino Speeduino - OEM-3 J: Rear O2 signal: no free o2_narrowband/analog_0_5 on Speeduino Speeduino - OEM-2 A: Fuel tank pressure: no free analog_0_5 on Speeduino Speeduino - OEM-3 K: Fuel level: no free analog_0_5 on Speeduino Speeduino - OEM-1 G: Power steering pressure switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-1 P: A/C request: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-1 V: Neutral switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-3 I: Clutch switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-3 M: ISC valve +14V feed: no rule for class switched_feed; wire by hand - OEM-3 T: 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 MX5NB1X install manual (NB1 1999-00) | https://linkecu.com/documentation/MX5XNB1.pdf | archive | 2026-10-05 | 2e36c91270cc |
| 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 | — | — | — | — |