MX-5 Miata NA6 1990-93 (B6-ZE, 1.6) → Speeduino Speeduino v0.4 (auto)
MX-5 Miata NA6 1990-93 (B6-ZE, 1.6) — Speeduino — Speeduino
⚠ NOT CHECKED. Don't build from this.
Drawn by Michael Gnankou · Rev 0 · draft · 2026-10-08
Before you start
| Status | draft · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | 1: read the Findings page before cutting any wire |
| Size of the job | 25 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 | OEM-2-C | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | OEM-2-D | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| 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-1-E | SPEEDUINO-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-2-I | SPEEDUINO-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-2-N | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-2-Q | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-2-P | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-1-C | SPEEDUINO-A-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-1-N | SPEEDUINO-A-14 | 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 |
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 | — | W24 | — | 0.5 | SPEEDUINO-A-18 | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | W19 | — | 0.5 | SPEEDUINO-A-15 | — | — | — |
| 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 | — | — | — |
| N | Wide-open throttle switch | — | W25 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| P | Power steering pressure switch | — | — | — | — | — | — | — | — |
| Q | A/C request | — | — | — | — | — | — | — | — |
| 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 | Power ground | — | W3 | — | 0.85 | SP-GND-1 | — | — | — |
| D | Power ground | — | W4 | — | 0.85 | SP-GND-1 | — | — | — |
| E | Crank position (CAS NE) | — | W11 | — | 0.5 | SPEEDUINO-A-25 | — | — | — |
| F | AFM ground | — | W7 | — | 0.5 | SP-0V-1 | — | — | — |
| G | Cam position (CAS G) | — | W12 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| I | Tachometer output | — | W20 | — | 0.5 | SPEEDUINO-A-17 | — | — | — |
| K | +5V sensor supply | — | W10 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
| L | Idle switch (TPS) | — | — | — | — | — | — | — | — |
| N | O2 sensor | — | W21 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| O | Air flow meter (AFM) | — | — | — | — | — | — | — | — |
| P | Intake air temperature (IAT) | — | W23 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
| Q | Coolant temperature (ECT) | — | W22 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| U | Injector 1 | — | W15 | — | 0.5 | SPEEDUINO-A-1 | — | — | — |
| V | Injector 2 | — | W16 | — | 0.5 | SPEEDUINO-A-2 | — | — | — |
| 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 | — | — | 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 | OEM-2-C | — | — | — |
| 1 | — | — | W4 | — | 0.85 | OEM-2-D | — | — | — |
| 1 | — | — | W5 | — | 0.85 | SPEEDUINO-A-10 | — | — | — |
| 1 | — | — | W6 | — | 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 | — | W5 | — | 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) | — | W25 | — | 0.5 | OEM-1-N | — | — | — |
| 15 | Proto area 2 (fan) | — | W19 | — | 0.5 | OEM-1-E | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | — | — | — | — | — | — | — |
| 17 | Proto area 4 (tachometer) | — | W20 | — | 0.5 | OEM-2-I | — | — | — |
| 18 | Proto area 5 (clutch) | — | W24 | — | 0.5 | OEM-1-C | — | — | — |
| 19 | Coolant temp (CLT) | — | W22 | — | 0.5 | OEM-2-Q | — | — | — |
| 2 | Injector 2 | — | W16 | — | 0.5 | OEM-2-V | — | — | — |
| 20 | Inlet air temp (IAT) | — | W23 | — | 0.5 | OEM-2-P | — | — | — |
| 21 | O2 sensor | — | W21 | — | 0.5 | OEM-2-N | — | — | — |
| 22 | TPS input | — | — | — | — | — | — | — | — |
| 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 | — | — | — | — | — | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | — | — | — | — | — | — | — |
| 37 | PWM idle | — | — | — | — | — | — | — | — |
| 38 | VVT | — | — | — | — | — | — | — | — |
| 5 | Injector 4 | — | W18 | — | 0.5 | OEM-2-Z | — | — | — |
| 7 | Ignition 1 | — | W13 | — | 0.5 | OEM-1-G | — | — | — |
| 8 | Ignition 4 | — | — | — | — | — | — | — | — |
| 9 | Ground | — | W6 | — | 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-C | Start signal | digital_in | SPEEDUINO-A-18 | Proto area 5 (clutch) | digital_in | single_source | |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | SPEEDUINO-A-15 | Proto area 2 (fan) | low_side_out | single_source | |
| OEM-1-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | single_source | |
| OEM-1-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | SPEEDUINO-A-34 | Ignition 2 | ignition_out | single_source | |
| OEM-1-N | Wide-open throttle switch | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | single_source | |
| OEM-1-P | Power steering pressure switch | digital_in | — | — | — | single_source | |
| OEM-1-Q | A/C request | digital_in | — | — | — | single_source | |
| OEM-1-V | Neutral/clutch switch | digital_in | — | — | — | single_source | |
| OEM-2-A | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-2-B | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-2-C | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-2-D | Power ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | single_source | |
| OEM-2-E | Crank position (CAS NE) | trigger_in | SPEEDUINO-A-25 | Crank input / VR1+ | trigger_in | single_source | |
| OEM-2-F | AFM ground | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | single_source | |
| OEM-2-G | Cam position (CAS G) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | single_source | |
| OEM-2-I | Tachometer output | tacho_out | SPEEDUINO-A-17 | Proto area 4 (tachometer) | tacho_out | single_source | |
| OEM-2-K | +5V sensor supply | vref | SPEEDUINO-A-13 | 5V | vref | single_source | |
| OEM-2-L | Idle switch (TPS) | digital_in | — | — | — | single_source | |
| OEM-2-N | O2 sensor | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | single_source | |
| OEM-2-O | Air flow meter (AFM) | analog_in | — | — | — | single_source | |
| OEM-2-P | Intake air temperature (IAT) | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | single_source | |
| OEM-2-Q | Coolant temperature (ECT) | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | single_source | |
| OEM-2-U | Injector 1 | injector_out | SPEEDUINO-A-1 | Injector 1 | injector_out | single_source | |
| OEM-2-V | Injector 2 | injector_out | SPEEDUINO-A-2 | Injector 2 | injector_out | single_source | |
| OEM-2-Y | Injector 3 | injector_out | SPEEDUINO-A-3 | Injector 3 | injector_out | single_source | |
| OEM-2-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-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 | OEM-2-C | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W4 | OEM-2-D | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W5 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | no route | Ground | — | |
| W6 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | no route | Ground | — | |
| W7 | OEM-2-F | SP-0V-1 | 0.5 | no route | AFM 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-1-E | SPEEDUINO-A-15 | 0.5 | no route | Malfunction indicator lamp (MIL) | — | |
| W20 | OEM-2-I | SPEEDUINO-A-17 | 0.5 | no route | Tachometer output | — | |
| W21 | OEM-2-N | SPEEDUINO-A-21 | 0.5 | no route | O2 sensor | — | |
| W22 | OEM-2-Q | SPEEDUINO-A-19 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W23 | OEM-2-P | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W24 | OEM-1-C | SPEEDUINO-A-18 | 0.5 | no route | Start signal | — | |
| W25 | OEM-1-N | SPEEDUINO-A-14 | 0.5 | no route | Wide-open throttle switch | — |
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 (2)
| 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. |
| info | UNMAPPED | OEM | 5 optional OEM pins are not mapped: OEM-1-P Power steering pressure switch; OEM-1-Q A/C request; OEM-1-V Neutral/clutch switch; OEM-2-L Idle switch (TPS); OEM-2-O Air flow meter (AFM) |
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 2026-10-06. 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-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 O: Air flow meter (AFM): no free maf/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-2 L: Idle switch (TPS): no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino
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 |