MX-5 Miata NA8 1994-95 (BP-ZE, 1.8, OBD-I) → Speeduino Speeduino v0.4 (auto)
MX-5 Miata NA8 1994-95 (BP-ZE, 1.8, OBD-I) — Speeduino — Speeduino
⚠ NOT CHECKED. Don't build from this.
Drawn by Michael Gnankou · Rev 0 · draft · 2026-10-12
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.
| 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 · 5 connectors · 2 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-2-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-2-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | OEM-2-C | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-2-D | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-2-F | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-2-K | SPEEDUINO-A-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-2-E | SPEEDUINO-A-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | OEM-2-G | SPEEDUINO-A-24 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-1-G | SPEEDUINO-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-1-H | SPEEDUINO-A-34 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-2-U | SPEEDUINO-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-2-V | SPEEDUINO-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-2-Y | SPEEDUINO-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-2-Z | SPEEDUINO-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-2-M | SPEEDUINO-A-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-2-Q | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-1-J | SPEEDUINO-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-1-R | SPEEDUINO-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-2-S | SPEEDUINO-A-36 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-2-T | SPEEDUINO-A-35 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-1-L | SPEEDUINO-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-2-L | SPEEDUINO-A-38 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-2-I | SPEEDUINO-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-2-N | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-2-P | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-1-M | SPEEDUINO-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-1-C | SPEEDUINO-A-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ |
Bench test (before first power-up)
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-10 | SPEEDUINO-A-13 | open (OL) | power ground must not touch 5 V sensor reference | |
| 2 | SPEEDUINO-A-12 | SPEEDUINO-A-13 | open (OL) | sensor 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-1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Constant +12V | — | — | — | — | — | — | — | — |
| B | ECU power +14V (main relay) | — | — | — | — | — | — | — | — |
| C | Start signal | — | W31 | — | 0.5 | SPEEDUINO-A-18 | — | — | — |
| D | Data link connector | — | — | — | — | — | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | — | — | — | — | — | — | — |
| G | Ignition 1 (coils 1+4, wasted spark) | — | W13 | — | 0.5 | SPEEDUINO-A-7 | — | — | — |
| H | Ignition 2 (coils 2+3, wasted spark) | — | W14 | — | 0.5 | SPEEDUINO-A-34 | — | — | — |
| I | Powertrain control module (transmission) | — | — | — | — | — | — | — | — |
| J | A/C relay | — | W21 | — | 0.5 | SPEEDUINO-A-16 | — | — | — |
| L | Coolant fan relay | — | W25 | — | 0.5 | SPEEDUINO-A-37 | — | — | — |
| M | Vehicle speed | — | W30 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| N | Powertrain control module (transmission) | — | — | — | — | — | — | — | — |
| O | Stop light switch | — | — | — | — | — | — | — | — |
| P | Power steering pressure switch | — | — | — | — | — | — | — | — |
| Q | A/C request | — | — | — | — | — | — | — | — |
| R | Cooling fan relay | — | W22 | — | 0.5 | SPEEDUINO-A-15 | — | — | — |
| S | Heater control unit | — | — | — | — | — | — | — | — |
| T | Unknown | — | — | — | — | — | — | — | — |
| U | Unknown | — | — | — | — | — | — | — | — |
| V | Neutral/clutch switch | — | — | — | — | — | — | — | — |
OEM-2
| 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 | Sensor ground (E2) | — | W5 | — | 0.5 | SP-0V-1 | — | — | — |
| D | Sensor ground (E2) | — | W6 | — | 0.5 | SP-0V-1 | — | — | — |
| E | Crank position (CAS NE) | — | W11 | — | 0.5 | SPEEDUINO-A-25 | — | — | — |
| F | MAF ground | — | W7 | — | 0.5 | SP-0V-1 | — | — | — |
| G | Cam position (CAS G) | — | W12 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| H | Data link connector | — | — | — | — | — | — | — | — |
| I | Tachometer output | — | W27 | — | 0.5 | SPEEDUINO-A-17 | — | — | — |
| J | EGR function sensor | — | — | — | — | — | — | — | — |
| K | +5V sensor supply | — | W10 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
| L | Rear defroster relay | — | W26 | — | 0.5 | SPEEDUINO-A-38 | — | — | — |
| M | Throttle position (TPS) | — | W19 | — | 0.5 | SPEEDUINO-A-22 | — | — | — |
| N | O2 sensor | — | W28 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| O | Mass air flow (MAF) | — | — | — | — | — | — | — | — |
| P | Intake air temperature (IAT) | — | W29 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
| Q | Coolant temperature (ECT) | — | W20 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| R | PRC solenoid (fuel pressure regulator) | — | — | — | — | — | — | — | — |
| S | Condenser fan relay | — | W23 | — | 0.5 | SPEEDUINO-A-36 | — | — | — |
| T | Fuel pump relay | — | W24 | — | 0.5 | SPEEDUINO-A-35 | — | — | — |
| U | Injector 1 | — | W15 | — | 0.5 | SPEEDUINO-A-1 | — | — | — |
| V | Injector 2 | — | W16 | — | 0.5 | SPEEDUINO-A-2 | — | — | — |
| W | ISC solenoid | — | — | — | — | — | — | — | — |
| X | Evap purge solenoid | — | — | — | — | — | — | — | — |
| Y | Injector 3 | — | W17 | — | 0.5 | SPEEDUINO-A-3 | — | — | — |
| Z | Injector 4 | — | W18 | — | 0.5 | SPEEDUINO-A-5 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W5 | — | 0.5 | OEM-2-C | — | — | — |
| 1 | — | — | W6 | — | 0.5 | OEM-2-D | — | — | — |
| 1 | — | — | W7 | — | 0.5 | OEM-2-F | — | — | — |
| 1 | — | — | W8 | — | 0.5 | SPEEDUINO-A-12 | — | — | — |
| 1 | — | — | W9 | — | 0.5 | SPEEDUINO-A-23 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-2-A | — | — | — |
| 1 | — | — | W2 | — | 0.85 | OEM-2-B | — | — | — |
| 1 | — | — | W3 | — | 0.85 | SPEEDUINO-A-10 | — | — | — |
| 1 | — | — | W4 | — | 0.85 | SPEEDUINO-A-9 | — | — | — |
SPEEDUINO-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Injector 1 | — | W15 | — | 0.5 | OEM-2-U | — | — | — |
| 10 | Ground | — | W3 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | MAP sensor (0-5V) | — | — | — | — | — | — | — | — |
| 12 | Ground | — | W8 | — | 0.5 | SP-0V-1 | — | — | — |
| 13 | 5V | — | W10 | — | 0.5 | OEM-2-K | — | — | — |
| 14 | Proto area 1 (flex fuel) | — | W30 | — | 0.5 | OEM-1-M | — | — | — |
| 15 | Proto area 2 (fan) | — | W22 | — | 0.5 | OEM-1-R | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | W21 | — | 0.5 | OEM-1-J | — | — | — |
| 17 | Proto area 4 (tachometer) | — | W27 | — | 0.5 | OEM-2-I | — | — | — |
| 18 | Proto area 5 (clutch) | — | W31 | — | 0.5 | OEM-1-C | — | — | — |
| 19 | Coolant temp (CLT) | — | W20 | — | 0.5 | OEM-2-Q | — | — | — |
| 2 | Injector 2 | — | W16 | — | 0.5 | OEM-2-V | — | — | — |
| 20 | Inlet air temp (IAT) | — | W29 | — | 0.5 | OEM-2-P | — | — | — |
| 21 | O2 sensor | — | W28 | — | 0.5 | OEM-2-N | — | — | — |
| 22 | TPS input | — | W19 | — | 0.5 | OEM-2-M | — | — | — |
| 23 | Ground | — | W9 | — | 0.5 | SP-0V-1 | — | — | — |
| 24 | Cam input / VR2+ | — | W12 | — | 0.5 | OEM-2-G | — | — | — |
| 25 | Crank input / VR1+ | — | W11 | — | 0.5 | OEM-2-E | — | — | — |
| 26 | VR2- | — | — | — | — | — | — | — | — |
| 27 | VR1- | — | — | — | — | — | — | — | — |
| 28 | 5V | — | — | — | — | — | — | — | — |
| 29 | Idle stepper 2B | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | W17 | — | 0.5 | OEM-2-Y | — | — | — |
| 30 | Idle stepper 2A | — | — | — | — | — | — | — | — |
| 31 | Idle stepper 1A | — | — | — | — | — | — | — | — |
| 32 | Idle stepper 1B | — | — | — | — | — | — | — | — |
| 33 | Ignition 3 | — | — | — | — | — | — | — | — |
| 34 | Ignition 2 | — | W14 | — | 0.5 | OEM-1-H | — | — | — |
| 35 | Boost | — | W24 | — | 0.5 | OEM-2-T | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | W23 | — | 0.5 | OEM-2-S | — | — | — |
| 37 | PWM idle | — | W25 | — | 0.5 | OEM-1-L | — | — | — |
| 38 | VVT | — | W26 | — | 0.5 | OEM-2-L | — | — | — |
| 5 | Injector 4 | — | W18 | — | 0.5 | OEM-2-Z | — | — | — |
| 7 | Ignition 1 | — | W13 | — | 0.5 | OEM-1-G | — | — | — |
| 8 | Ignition 4 | — | — | — | — | — | — | — | — |
| 9 | Ground | — | W4 | — | 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 | — | — | — | LR | single_source |
| OEM-1-B | ECU power +14V (main relay) | power_in | — | — | — | WR | single_source |
| OEM-1-C | Start signal | digital_in | SPEEDUINO-A-18 | Proto area 5 (clutch) | digital_in | V | single_source |
| OEM-1-D | Data link connector | serial | — | — | — | WG | single_source |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | — | — | — | YB | single_source |
| OEM-1-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | BrY | single_source |
| OEM-1-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | SPEEDUINO-A-34 | Ignition 2 | ignition_out | Br | single_source |
| OEM-1-I | Powertrain control module (transmission) | — | — | — | — | LW | single_source |
| OEM-1-J | A/C relay | low_side_out | SPEEDUINO-A-16 | Proto area 3 (fuel pump) | low_side_out | single_source | |
| OEM-1-L | Coolant fan relay | low_side_out | SPEEDUINO-A-37 | PWM idle | low_side_out | BG | single_source |
| OEM-1-M | Vehicle speed | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | GR | single_source |
| OEM-1-N | Powertrain control module (transmission) | — | — | — | — | R | single_source |
| OEM-1-O | Stop light switch | digital_in | — | — | — | GB | single_source |
| OEM-1-P | Power steering pressure switch | digital_in | — | — | — | LY | single_source |
| OEM-1-Q | A/C request | digital_in | — | — | — | LgB | single_source |
| OEM-1-R | Cooling fan relay | low_side_out | SPEEDUINO-A-15 | Proto area 2 (fan) | low_side_out | YB | single_source |
| OEM-1-S | Heater control unit | — | — | — | — | LOr | single_source |
| OEM-1-T | Unknown | — | — | — | — | YR | single_source |
| OEM-1-U | Unknown | — | — | — | — | RB | single_source |
| OEM-1-V | Neutral/clutch switch | digital_in | — | — | — | BrW | single_source |
| OEM-2-A | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | B | single_source |
| OEM-2-B | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | B | single_source |
| OEM-2-C | Sensor ground (E2) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | BLg | corroborated |
| OEM-2-D | Sensor ground (E2) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | BL | corroborated |
| OEM-2-E | Crank position (CAS NE) | trigger_in | SPEEDUINO-A-25 | Crank input / VR1+ | trigger_in | W | single_source |
| OEM-2-F | MAF ground | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | BR | single_source |
| OEM-2-G | Cam position (CAS G) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | YL | single_source |
| OEM-2-H | Data link connector | serial | — | — | — | LgY | single_source |
| OEM-2-I | Tachometer output | tacho_out | SPEEDUINO-A-17 | Proto area 4 (tachometer) | tacho_out | BW | single_source |
| OEM-2-J | EGR function sensor | — | — | — | — | LgR | single_source |
| OEM-2-K | +5V sensor supply | vref | SPEEDUINO-A-13 | 5V | vref | LgW | single_source |
| OEM-2-L | Rear defroster relay | low_side_out | SPEEDUINO-A-38 | VVT | low_side_out | LR | single_source |
| OEM-2-M | Throttle position (TPS) | analog_in | SPEEDUINO-A-22 | TPS input | analog_in | RB | single_source |
| OEM-2-N | O2 sensor | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | RL | single_source |
| OEM-2-O | Mass air flow (MAF) | analog_in | — | — | — | R | single_source |
| OEM-2-P | Intake air temperature (IAT) | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | RB | single_source |
| OEM-2-Q | Coolant temperature (ECT) | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | LW | single_source |
| OEM-2-R | PRC solenoid (fuel pressure regulator) | low_side_out | — | — | — | YG | single_source |
| OEM-2-S | Condenser fan relay | low_side_out | SPEEDUINO-A-36 | Idle 2 (3-wire idle) | low_side_out | LW | single_source |
| OEM-2-T | Fuel pump relay | low_side_out | SPEEDUINO-A-35 | Boost | low_side_out | Lg | single_source |
| OEM-2-U | Injector 1 | injector_out | SPEEDUINO-A-1 | Injector 1 | injector_out | Y | single_source |
| OEM-2-V | Injector 2 | injector_out | SPEEDUINO-A-2 | Injector 2 | injector_out | YB | single_source |
| OEM-2-W | ISC solenoid | low_side_out | — | — | — | LOr | single_source |
| OEM-2-X | Evap purge solenoid | low_side_out | — | — | — | YR | single_source |
| OEM-2-Y | Injector 3 | injector_out | SPEEDUINO-A-3 | Injector 3 | injector_out | GW | single_source |
| OEM-2-Z | Injector 4 | injector_out | SPEEDUINO-A-5 | Injector 4 | injector_out | G | single_source |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-2-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W2 | OEM-2-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W3 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | no route | Ground | — | |
| W4 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | no route | Ground | — | |
| W5 | OEM-2-C | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W6 | OEM-2-D | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W7 | OEM-2-F | SP-0V-1 | 0.5 | no route | MAF ground | — | |
| W8 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | no route | Ground | — | |
| W9 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | no route | Ground | — | |
| W10 | OEM-2-K | SPEEDUINO-A-13 | 0.5 | no route | +5V sensor supply | — | |
| W11 | OEM-2-E | SPEEDUINO-A-25 | 0.5 | no route | Crank position (CAS NE) | — | |
| W12 | OEM-2-G | SPEEDUINO-A-24 | 0.5 | no route | Cam position (CAS G) | — | |
| W13 | OEM-1-G | SPEEDUINO-A-7 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W14 | OEM-1-H | SPEEDUINO-A-34 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W15 | OEM-2-U | SPEEDUINO-A-1 | 0.5 | no route | Injector 1 | — | |
| W16 | OEM-2-V | SPEEDUINO-A-2 | 0.5 | no route | Injector 2 | — | |
| W17 | OEM-2-Y | SPEEDUINO-A-3 | 0.5 | no route | Injector 3 | — | |
| W18 | OEM-2-Z | SPEEDUINO-A-5 | 0.5 | no route | Injector 4 | — | |
| W19 | OEM-2-M | SPEEDUINO-A-22 | 0.5 | no route | Throttle position (TPS) | — | |
| W20 | OEM-2-Q | SPEEDUINO-A-19 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W21 | OEM-1-J | SPEEDUINO-A-16 | 0.5 | no route | A/C relay | — | |
| W22 | OEM-1-R | SPEEDUINO-A-15 | 0.5 | no route | Cooling fan relay | — | |
| W23 | OEM-2-S | SPEEDUINO-A-36 | 0.5 | no route | Condenser fan relay | — | |
| W24 | OEM-2-T | SPEEDUINO-A-35 | 0.5 | no route | Fuel pump relay | — | |
| W25 | OEM-1-L | SPEEDUINO-A-37 | 0.5 | no route | Coolant fan relay | — | |
| W26 | OEM-2-L | SPEEDUINO-A-38 | 0.5 | no route | Rear defroster relay | — | |
| W27 | OEM-2-I | SPEEDUINO-A-17 | 0.5 | no route | Tachometer output | — | |
| W28 | OEM-2-N | SPEEDUINO-A-21 | 0.5 | no route | O2 sensor | — | |
| W29 | OEM-2-P | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W30 | OEM-1-M | SPEEDUINO-A-14 | 0.5 | no route | Vehicle speed | — | |
| W31 | OEM-1-C | SPEEDUINO-A-18 | 0.5 | no route | Start signal | — |
Bill of materials
| Category | Part number | Manufacturer | Description | Qty | Unit |
|---|---|---|---|---|---|
| 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 (7)
| 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-O | 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-J A/C 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-T 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-S Condenser fan relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| info | UNMAPPED | OEM | 16 optional OEM pins are not mapped: OEM-1-D Data link connector; OEM-1-E Malfunction indicator lamp (MIL); OEM-1-I Powertrain control module (transmission); OEM-1-N Powertrain control module (transmission); OEM-1-O Stop light switch; OEM-1-P Power steering pressure switch; OEM-1-Q A/C request; OEM-1-S Heater control unit; OEM-1-T Unknown; OEM-1-U Unknown; OEM-1-V Neutral/clutch switch; OEM-2-H Data link connector; OEM-2-J EGR function sensor; OEM-2-R PRC solenoid (fuel pressure regulator); OEM-2-W ISC solenoid; OEM-2-X Evap purge solenoid |
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 2026-10-11. 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-2 O: 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 W: ISC solenoid: no free low_side/relay_control/heater_low_side/ls_hs/injector rated ≥ 1.0 A on Speeduino Speeduino - OEM-1 E: Malfunction indicator lamp (MIL): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 R: PRC solenoid (fuel pressure regulator): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-2 X: Evap purge solenoid: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-1 O: Stop light switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-1 P: Power steering pressure switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-1 Q: A/C request: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-1 V: Neutral/clutch switch: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino - OEM-1 D: Data link connector: no free k_line on Speeduino Speeduino - OEM-2 H: Data link connector: no free k_line on Speeduino Speeduino - OEM-1 I: Powertrain control module (transmission): not classified in the library; wire by hand - OEM-1 N: Powertrain control module (transmission): not classified in the library; wire by hand - OEM-1 S: Heater control unit: not classified in the library; wire by hand - OEM-1 T: Unknown: not classified in the library; wire by hand - OEM-1 U: Unknown: not classified in the library; wire by hand - OEM-2 J: EGR function sensor: not classified in the library; wire by hand
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | vendor_doc | Link G4X MX5X install manual (NA 1.6/1.8) | https://linkecu.com/documentation/MX5X.pdf | archive | 2026-10-05 | b7f730de9f6e |
| 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 | — | — | — | — |
| 2 | community_copy | rusefi wiki: 1994 Mazda Miata 1.8 (NA8) ECU pinout | https://github.com/rusefi/rusefi/wiki/Mazda-Miata-1994 | — | 2026-10-08 | 075801b907f4 |