MX-5 Miata NA6 1990-93 (B6-ZE, 1.6) → MoTeC M190 13190 (auto)
MX-5 Miata NA6 1990-93 (B6-ZE, 1.6) — MoTeC — M190
⚠ NOT CHECKED. Don't build from this.
Drawn by Michael Gnankou · Rev 0 · draft · 2026-10-09
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.
- Cut the sensor-ground-to-chassis wirerequired
Cut the wire in the engine bay that ties the ECU sensor/signal ground (2C/2D, BLK/LT GRN) to chassis ground, so the standalone gets a clean sensor-ground reference. After cutting, verify with a meter: sensor ground ↔ chassis ground reads open (OL) unless the standalone manual says otherwise.
Why: The stock loom bonds sensor ground to chassis ground; a standalone ECU needs its sensor ground isolated from the noisy chassis/power ground, otherwise sensor readings are noisy or wrong.
Where: Engine-bay ground joint near the ECU (1991 EWD Fig.2 shows the sensor-ground run and its joint connector).
Correction reported by Justin Barrera
Unverified — reported by Justin Barrera (Motorsport Wiring Alliance), not yet sourced.
- Bypass the airflow-meter pump switchrecommended
The stock pump is run by the flapper airflow meter's pump-switch contact through the circuit-opening relay, not by the ECU. The standalone harness adds ECU control of the pump relay (ignition-switched, fused); remove/bypass the AFM pump switch so the two do not fight.
Why: There is no stock fuel-pump output at the ECU, so the standalone provides it. Leaving the AFM switch in place leaves a second, unswitched pump path.
Where: Airflow meter connector (pump-switch contact) and circuit-opening relay.
Correction reported by Justin Barrera
Source: 1991 Mazda Miata wiring diagrams (Mitchell reproduction, mellens.net community mirror)
| Status | draft · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | none |
| Size of the job | 43 wires · 8 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-1-B | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | SP-14V-1 | M190-B-H | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-14V-1 | M190-B-J | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-14V-1 | M190-B-K | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | SP-14V-1 | M190-B-L | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-1-A | M190-A-38 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-2-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | OEM-2-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | SP-GND-1 | M190-B-G | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | SP-GND-1 | M190-B-W | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | SP-GND-1 | M190-B-X | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | SP-GND-1 | M190-B-Y | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | SP-GND-1 | M190-B-Z | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | SP-GND-1 | M190-B-c | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-2-C | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-2-D | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | SP-0V-1 | M190-A-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | SP-0V-1 | M190-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | SP-0V-1 | M190-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | SP-0V-1 | M190-C-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | SP-0V-1 | M190-C-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | SP-0V-1 | M190-C-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | SP-0V-1 | M190-C-30 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-2-K | M190-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-2-E | M190-C-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-2-G | M190-C-32 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-1-G | M190-C-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-1-H | M190-C-8 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-2-U | M190-A-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-2-V | M190-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-2-Y | M190-B-U | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-2-Z | M190-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-1-E | M190-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-2-O | M190-C-42 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-2-N | M190-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-2-Q | M190-C-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-2-P | M190-C-39 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-1-C | M190-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-1-N | M190-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-1-P | M190-A-30 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W41 | OEM-1-Q | M190-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W42 | OEM-1-V | M190-C-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W43 | OEM-2-L | M190-C-27 | 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): Cut the sensor-ground-to-chassis wire.
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 | M190-A-38 | M190-A-18 | open (OL) | +12 V supply must not touch sensor ground | |
| 2 | M190-A-38 | M190-B-G | open (OL) | +12 V supply must not touch power ground | |
| 3 | M190-B-H | M190-A-18 | open (OL) | +12 V supply must not touch sensor ground | |
| 4 | M190-B-H | M190-B-G | open (OL) | +12 V supply must not touch power ground | |
| 5 | M190-A-18 | M190-A-16 | open (OL) | sensor ground must not touch 5 V sensor reference | |
| 6 | M190-A-38 | M190-A-16 | open (OL) | +12 V supply must not touch 5 V sensor reference | |
| 7 | M190-B-G | M190-A-16 | open (OL) | power ground must not touch 5 V sensor reference | |
| 8 | M190-B-H | M190-A-16 | open (OL) | +12 V supply 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
M190-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Low Side Injector 3 | — | — | — | — | — | — | — | — |
| 10 | Low Side Injector 8 | — | — | — | — | — | — | — | — |
| 11 | Peak Hold Injector 1 | — | W29 | — | 0.5 | OEM-2-U | — | — | — |
| 12 | Peak Hold Injector 2 | — | W32 | — | 0.5 | OEM-2-Z | — | — | — |
| 13 | Analogue Voltage Input 11 | — | — | — | — | — | — | — | — |
| 14 | Digital Input 2 | — | W39 | — | 0.5 | OEM-1-N | — | — | — |
| 15 | RS232 Receive | — | — | — | — | — | — | — | — |
| 16 | Sensor 5.0V C3 | — | W24 | — | 0.5 | OEM-2-K | — | — | — |
| 17 | Low Side Injector 11 | — | — | — | — | — | — | — | — |
| 18 | Sensor 0V C1 | — | W17 | — | 0.5 | SP-0V-1 | — | — | — |
| 19 | Sensor 0V C2 | — | W18 | — | 0.5 | SP-0V-1 | — | — | — |
| 2 | Low Side Injector 2 | — | W33 | — | 0.5 | OEM-1-E | — | — | — |
| 20 | Sensor 0V C3 | — | W19 | — | 0.5 | SP-0V-1 | — | — | — |
| 21 | Digital Input 1 | — | W38 | — | 0.5 | OEM-1-C | — | — | — |
| 22 | LIN Bus | — | — | — | — | — | — | — | — |
| 23 | RS232 Transmit | — | — | — | — | — | — | — | — |
| 24 | CAN Bus 2 High | — | — | — | — | — | — | — | — |
| 25 | Low Side Injector 7 | — | — | — | — | — | — | — | — |
| 26 | Peak Hold Injector 3 | — | — | — | — | — | — | — | — |
| 27 | Analogue Voltage Input 15 | — | — | — | — | — | — | — | — |
| 28 | Analogue Voltage Input 16 | — | — | — | — | — | — | — | — |
| 29 | Analogue Voltage Input 17 | — | — | — | — | — | — | — | — |
| 3 | Low Side Injector 1 | — | W30 | — | 0.5 | OEM-2-V | — | — | — |
| 30 | Digital Input 3 | — | W40 | — | 0.5 | OEM-1-P | — | — | — |
| 31 | CAN Bus 2 Low | — | — | — | — | — | — | — | — |
| 32 | Low Side Injector 10 | — | — | — | — | — | — | — | — |
| 33 | Peak Hold Injector 4 | — | — | — | — | — | — | — | — |
| 34 | Analogue Voltage Input 13 | — | — | — | — | — | — | — | — |
| 35 | Analogue Voltage Input 12 | — | — | — | — | — | — | — | — |
| 36 | Peak Hold Injector 7 | — | — | — | — | — | — | — | — |
| 37 | Digital Input 4 | — | W41 | — | 0.5 | OEM-1-Q | — | — | — |
| 38 | Battery Backup | — | W6 | — | 0.85 | OEM-1-A | — | — | — |
| 39 | CAN Bus 3 High | — | — | — | — | — | — | — | — |
| 4 | Low Side Injector 12 | — | — | — | — | — | — | — | — |
| 40 | Low Side Injector 6 | — | — | — | — | — | — | — | — |
| 41 | Analogue Voltage Input 14 | — | — | — | — | — | — | — | — |
| 42 | Peak Hold Injector 9 | — | — | — | — | — | — | — | — |
| 43 | Peak Hold Injector 10 | — | — | — | — | — | — | — | — |
| 44 | Peak Hold Injector 6 | — | — | — | — | — | — | — | — |
| 45 | Peak Hold Injector 5 | — | — | — | — | — | — | — | — |
| 46 | CAN Bus 3 Low | — | — | — | — | — | — | — | — |
| 47 | Low Side Injector 9 | — | — | — | — | — | — | — | — |
| 48 | Low Side Injector 5 | — | — | — | — | — | — | — | — |
| 49 | Peak Hold Injector 11 | — | — | — | — | — | — | — | — |
| 5 | Low Side Injector 4 | — | — | — | — | — | — | — | — |
| 50 | Peak Hold Injector 12 | — | — | — | — | — | — | — | — |
| 51 | Peak Hold Injector 8 | — | — | — | — | — | — | — | — |
| 52 | Low Side Ignition 12 | — | — | — | — | — | — | — | — |
| 53 | Low Side Ignition 9 | — | — | — | — | — | — | — | — |
| 54 | Low Side Ignition 10 | — | — | — | — | — | — | — | — |
| 55 | Low Side Ignition 11 | — | — | — | — | — | — | — | — |
| 6 | Lambda Narrow Input 2 | — | — | — | — | — | — | — | — |
| 7 | Lambda Narrow Input 1 | — | W35 | — | 0.5 | OEM-2-N | — | — | — |
| 8 | Sensor 5.0V C1 | — | — | — | — | — | — | — | — |
| 9 | Sensor 5.0V C2 | — | — | — | — | — | — | — | — |
M190-B
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Half Bridge Output 1 | — | — | — | — | — | — | — | — |
| B | Half Bridge Output 2 | — | — | — | — | — | — | — | — |
| C | Half Bridge Output 3 | — | — | — | — | — | — | — | — |
| D | Half Bridge Output 4 | — | — | — | — | — | — | — | — |
| E | Half Bridge Output 5 | — | — | — | — | — | — | — | — |
| F | Half Bridge Output 6 | — | — | — | — | — | — | — | — |
| G | Battery Negative 1 | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
| H | Battery Positive 1 | — | W2 | — | 0.85 | SP-14V-1 | — | — | — |
| J | Battery Positive 2 | — | W3 | — | 0.85 | SP-14V-1 | — | — | — |
| K | Battery Positive 3 | — | W4 | — | 0.85 | SP-14V-1 | — | — | — |
| L | Battery Positive 4 | — | W5 | — | 0.85 | SP-14V-1 | — | — | — |
| M | Half Bridge Output 10 | — | — | — | — | — | — | — | — |
| N | Half Bridge Output 9 | — | — | — | — | — | — | — | — |
| P | Half Bridge Output 8 | — | — | — | — | — | — | — | — |
| R | Half Bridge Output 7 | — | — | — | — | — | — | — | — |
| S | Low Side Injector 4 | — | — | — | — | — | — | — | — |
| T | Low Side Injector 6 | — | — | — | — | — | — | — | — |
| U | Low Side Injector 1 | — | W31 | — | 0.5 | OEM-2-Y | — | — | — |
| V | Low Side Injector 2 | — | — | — | — | — | — | — | — |
| W | Battery Negative 2 | — | W10 | — | 0.85 | SP-GND-1 | — | — | — |
| X | Battery Negative 3 | — | W11 | — | 0.85 | SP-GND-1 | — | — | — |
| Y | Battery Negative 4 | — | W12 | — | 0.85 | SP-GND-1 | — | — | — |
| Z | Battery Negative 5 | — | W13 | — | 0.85 | SP-GND-1 | — | — | — |
| a | Low Side Injector 5 | — | — | — | — | — | — | — | — |
| b | Low Side Injector 3 | — | — | — | — | — | — | — | — |
| c | Battery Negative 6 | — | W14 | — | 0.85 | SP-GND-1 | — | — | — |
M190-C
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Low Side Ignition 4 | — | — | — | — | — | — | — | — |
| 10 | Universal Digital Input 8 | — | — | — | — | — | — | — | — |
| 11 | Analogue Voltage Input 6 | — | — | — | — | — | — | — | — |
| 12 | Analogue Voltage Input 7 | — | — | — | — | — | — | — | — |
| 13 | Analogue Voltage Input 9 | — | — | — | — | — | — | — | — |
| 14 | Sensor 0V A1 | — | W20 | — | 0.5 | SP-0V-1 | — | — | — |
| 15 | Sensor 0V A2 | — | W21 | — | 0.5 | SP-0V-1 | — | — | — |
| 16 | Low Side Ignition 1 | — | W27 | — | 0.5 | OEM-1-G | — | — | — |
| 17 | Universal Digital Input 7 | — | — | — | — | — | — | — | — |
| 18 | Universal Digital Input 1 | — | W25 | — | 0.5 | OEM-2-E | — | — | — |
| 19 | Universal Digital Input 12 | — | — | — | — | — | — | — | — |
| 2 | Low Side Ignition 3 | — | — | — | — | — | — | — | — |
| 20 | Universal Digital Input 11 | — | — | — | — | — | — | — | — |
| 21 | Universal Digital Input 10 | — | — | — | — | — | — | — | — |
| 22 | Universal Digital Input 9 | — | — | — | — | — | — | — | — |
| 23 | Sensor 0V B1 | — | W22 | — | 0.5 | SP-0V-1 | — | — | — |
| 24 | CAN Bus 1 High | — | — | — | — | — | — | — | — |
| 25 | Universal Digital Input 3 | — | W42 | — | 0.5 | OEM-1-V | — | — | — |
| 26 | Ethernet Receive - | — | — | — | — | — | — | — | — |
| 27 | Universal Digital Input 4 | — | W43 | — | 0.5 | OEM-2-L | — | — | — |
| 28 | Analogue Voltage Input 4 | — | — | — | — | — | — | — | — |
| 29 | Analogue Voltage Input 5 | — | — | — | — | — | — | — | — |
| 3 | Low Side Ignition 8 | — | — | — | — | — | — | — | — |
| 30 | Sensor 0V B2 | — | W23 | — | 0.5 | SP-0V-1 | — | — | — |
| 31 | CAN Bus 1 Low | — | — | — | — | — | — | — | — |
| 32 | Universal Digital Input 2 | — | W26 | — | 0.5 | OEM-2-G | — | — | — |
| 33 | Ethernet Receive + | — | — | — | — | — | — | — | — |
| 34 | Ethernet Transmit - | — | — | — | — | — | — | — | — |
| 35 | Analogue Voltage Input 3 | — | — | — | — | — | — | — | — |
| 36 | Analogue Voltage Input 2 | — | — | — | — | — | — | — | — |
| 37 | Analogue Temperature Input 1 | — | W36 | — | 0.5 | OEM-2-Q | — | — | — |
| 38 | Analogue Temperature Input 3 | — | — | — | — | — | — | — | — |
| 39 | Analogue Temperature Input 2 | — | W37 | — | 0.5 | OEM-2-P | — | — | — |
| 4 | Low Side Ignition 6 | — | — | — | — | — | — | — | — |
| 40 | Universal Digital Input 5 | — | — | — | — | — | — | — | — |
| 41 | Ethernet Transmit + | — | — | — | — | — | — | — | — |
| 42 | Analogue Voltage Input 1 | — | W34 | — | 0.5 | OEM-2-O | — | — | — |
| 43 | Knock Input 3 | — | — | — | — | — | — | — | — |
| 44 | Knock Input 2 | — | — | — | — | — | — | — | — |
| 45 | Analogue Temperature Input 5 | — | — | — | — | — | — | — | — |
| 46 | Analogue Temperature Input 4 | — | — | — | — | — | — | — | — |
| 47 | Universal Digital Input 6 | — | — | — | — | — | — | — | — |
| 48 | Sensor 5.0V A1 | — | — | — | — | — | — | — | — |
| 49 | Knock Input 4 | — | — | — | — | — | — | — | — |
| 5 | Low Side Ignition 5 | — | — | — | — | — | — | — | — |
| 50 | Sensor 5.0V B1 | — | — | — | — | — | — | — | — |
| 51 | Knock Input 1 | — | — | — | — | — | — | — | — |
| 52 | Analogue Temperature Input 6 | — | — | — | — | — | — | — | — |
| 53 | Sensor 5.0V A2 | — | — | — | — | — | — | — | — |
| 54 | Sensor 6.3V | — | — | — | — | — | — | — | — |
| 55 | Sensor 5.0V B2 | — | — | — | — | — | — | — | — |
| 6 | Analogue Voltage Input 8 | — | — | — | — | — | — | — | — |
| 7 | Analogue Voltage Input 10 | — | — | — | — | — | — | — | — |
| 8 | Low Side Ignition 2 | — | W28 | — | 0.5 | OEM-1-H | — | — | — |
| 9 | Low Side Ignition 7 | — | — | — | — | — | — | — | — |
OEM-1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Constant +12V | — | W6 | — | 0.85 | M190-A-38 | — | — | — |
| B | ECU power +14V (main relay) | — | W1 | — | 0.85 | SP-14V-1 | — | — | — |
| C | Start signal | — | W38 | — | 0.5 | M190-A-21 | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | W33 | — | 0.5 | M190-A-2 | — | — | — |
| G | Ignition 1 (coils 1+4, wasted spark) | — | W27 | — | 0.5 | M190-C-16 | — | — | — |
| H | Ignition 2 (coils 2+3, wasted spark) | — | W28 | — | 0.5 | M190-C-8 | — | — | — |
| N | Wide-open throttle switch | — | W39 | — | 0.5 | M190-A-14 | — | — | — |
| P | Power steering pressure switch | — | W40 | — | 0.5 | M190-A-30 | — | — | — |
| Q | A/C request | — | W41 | — | 0.5 | M190-A-37 | — | — | — |
| V | Neutral/clutch switch | — | W42 | — | 0.5 | M190-C-25 | — | — | — |
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W7 | — | 0.85 | SP-GND-1 | — | — | — |
| B | Power ground | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| C | Sensor ground (E2) | — | W15 | — | 0.5 | SP-0V-1 | — | — | — |
| D | Sensor ground (E2) | — | W16 | — | 0.5 | SP-0V-1 | — | — | — |
| E | Crank position (CAS NE) | — | W25 | — | 0.5 | M190-C-18 | — | — | — |
| F | NC | — | — | — | — | — | — | — | — |
| G | Cam position (CAS G) | — | W26 | — | 0.5 | M190-C-32 | — | — | — |
| I | Tachometer output | — | — | — | — | — | — | — | — |
| K | +5V sensor supply | — | W24 | — | 0.5 | M190-A-16 | — | — | — |
| L | Idle switch (TPS) | — | W43 | — | 0.5 | M190-C-27 | — | — | — |
| N | O2 sensor | — | W35 | — | 0.5 | M190-A-7 | — | — | — |
| O | Air flow meter (AFM) | — | W34 | — | 0.5 | M190-C-42 | — | — | — |
| P | Intake air temperature (IAT) | — | W37 | — | 0.5 | M190-C-39 | — | — | — |
| Q | Coolant temperature (ECT) | — | W36 | — | 0.5 | M190-C-37 | — | — | — |
| U | Injector 1 & 3 (batch) | — | W29 | — | 0.5 | M190-A-11 | — | — | — |
| V | Injector 2 & 4 (batch) | — | W30 | — | 0.5 | M190-A-3 | — | — | — |
| Y | Injector 3 (California sequential) | — | W31 | — | 0.5 | M190-B-U | — | — | — |
| Z | Injector 4 (California sequential) | — | W32 | — | 0.5 | M190-A-12 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W15 | — | 0.5 | OEM-2-C | — | — | — |
| 1 | — | — | W16 | — | 0.5 | OEM-2-D | — | — | — |
| 1 | — | — | W17 | — | 0.5 | M190-A-18 | — | — | — |
| 1 | — | — | W18 | — | 0.5 | M190-A-19 | — | — | — |
| 1 | — | — | W19 | — | 0.5 | M190-A-20 | — | — | — |
| 1 | — | — | W20 | — | 0.5 | M190-C-14 | — | — | — |
| 1 | — | — | W21 | — | 0.5 | M190-C-15 | — | — | — |
| 1 | — | — | W22 | — | 0.5 | M190-C-23 | — | — | — |
| 1 | — | — | W23 | — | 0.5 | M190-C-30 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-1-B | — | — | — |
| 1 | — | — | W2 | — | 0.85 | M190-B-H | — | — | — |
| 1 | — | — | W3 | — | 0.85 | M190-B-J | — | — | — |
| 1 | — | — | W4 | — | 0.85 | M190-B-K | — | — | — |
| 1 | — | — | W5 | — | 0.85 | M190-B-L | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W7 | — | 0.85 | OEM-2-A | — | — | — |
| 1 | — | — | W8 | — | 0.85 | OEM-2-B | — | — | — |
| 1 | — | — | W9 | — | 0.85 | M190-B-G | — | — | — |
| 1 | — | — | W10 | — | 0.85 | M190-B-W | — | — | — |
| 1 | — | — | W11 | — | 0.85 | M190-B-X | — | — | — |
| 1 | — | — | W12 | — | 0.85 | M190-B-Y | — | — | — |
| 1 | — | — | W13 | — | 0.85 | M190-B-Z | — | — | — |
| 1 | — | — | W14 | — | 0.85 | M190-B-c | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-1-A | Constant +12V | power_in | M190-A-38 | Battery Backup | power_in | single_source | |
| OEM-1-B | ECU power +14V (main relay) | power_in | M190-B-H + M190-B-J + M190-B-K + M190-B-L | Battery Positive 1 + Battery Positive 2 + Battery Positive 3 + Battery Positive 4 | power_in | single_source | |
| OEM-1-C | Start signal | digital_in | M190-A-21 | Digital Input 1 | digital_in | single_source | |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | M190-A-2 | Low Side Injector 2 | injector_out | single_source | |
| OEM-1-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | M190-C-16 | Low Side Ignition 1 | ignition_out | single_source | |
| OEM-1-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | M190-C-8 | Low Side Ignition 2 | ignition_out | single_source | |
| OEM-1-N | Wide-open throttle switch | digital_in | M190-A-14 | Digital Input 2 | digital_in | single_source | |
| OEM-1-P | Power steering pressure switch | digital_in | M190-A-30 | Digital Input 3 | digital_in | single_source | |
| OEM-1-Q | A/C request | digital_in | M190-A-37 | Digital Input 4 | digital_in | single_source | |
| OEM-1-V | Neutral/clutch switch | digital_in | M190-C-25 | Universal Digital Input 3 | digital_in | single_source | |
| OEM-2-A | Power ground | ground | M190-B-G + M190-B-W + M190-B-X + M190-B-Y + M190-B-Z + M190-B-c | Battery Negative 1 + Battery Negative 2 + Battery Negative 3 + Battery Negative 4 + Battery Negative 5 + Battery Negative 6 | ground | single_source | |
| OEM-2-B | Power ground | ground | M190-B-G + M190-B-W + M190-B-X + M190-B-Y + M190-B-Z + M190-B-c | Battery Negative 1 + Battery Negative 2 + Battery Negative 3 + Battery Negative 4 + Battery Negative 5 + Battery Negative 6 | ground | single_source | |
| OEM-2-C | Sensor ground (E2) | sensor_ground | M190-A-18 + M190-A-19 + M190-A-20 + M190-C-14 + M190-C-15 + M190-C-23 + M190-C-30 | Sensor 0V C1 + Sensor 0V C2 + Sensor 0V C3 + Sensor 0V A1 + Sensor 0V A2 + Sensor 0V B1 + Sensor 0V B2 | sensor_ground | corroborated | |
| OEM-2-D | Sensor ground (E2) | sensor_ground | M190-A-18 + M190-A-19 + M190-A-20 + M190-C-14 + M190-C-15 + M190-C-23 + M190-C-30 | Sensor 0V C1 + Sensor 0V C2 + Sensor 0V C3 + Sensor 0V A1 + Sensor 0V A2 + Sensor 0V B1 + Sensor 0V B2 | sensor_ground | corroborated | |
| OEM-2-E | Crank position (CAS NE) | trigger_in | M190-C-18 | Universal Digital Input 1 | digital_in | single_source | |
| OEM-2-F | NC | — | — | — | — | corroborated | |
| OEM-2-G | Cam position (CAS G) | trigger_in | M190-C-32 | Universal Digital Input 2 | digital_in | single_source | |
| OEM-2-I | Tachometer output | tacho_out | — | — | — | single_source | |
| OEM-2-K | +5V sensor supply | vref | M190-A-16 | Sensor 5.0V C3 | vref | single_source | |
| OEM-2-L | Idle switch (TPS) | digital_in | M190-C-27 | Universal Digital Input 4 | digital_in | single_source | |
| OEM-2-N | O2 sensor | lambda_nb_in | M190-A-7 | Lambda Narrow Input 1 | lambda_nb_in | single_source | |
| OEM-2-O | Air flow meter (AFM) | analog_in | M190-C-42 | Analogue Voltage Input 1 | analog_in | single_source | |
| OEM-2-P | Intake air temperature (IAT) | temp_in | M190-C-39 | Analogue Temperature Input 2 | temp_in | single_source | |
| OEM-2-Q | Coolant temperature (ECT) | temp_in | M190-C-37 | Analogue Temperature Input 1 | temp_in | single_source | |
| OEM-2-U | Injector 1 & 3 (batch) | injector_out | M190-A-11 | Peak Hold Injector 1 | injector_out | corroborated | |
| OEM-2-V | Injector 2 & 4 (batch) | injector_out | M190-A-3 | Low Side Injector 1 | injector_out | corroborated | |
| OEM-2-Y | Injector 3 (California sequential) | injector_out | M190-B-U | Low Side Injector 1 | injector_out | corroborated | |
| OEM-2-Z | Injector 4 (California sequential) | injector_out | M190-A-12 | Peak Hold Injector 2 | injector_out | corroborated |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-1-B | SP-14V-1 | 0.85 | no route | ECU power +14V (main relay) | — | |
| W2 | SP-14V-1 | M190-B-H | 0.85 | no route | Battery Positive 1 | — | |
| W3 | SP-14V-1 | M190-B-J | 0.85 | no route | Battery Positive 2 | — | |
| W4 | SP-14V-1 | M190-B-K | 0.85 | no route | Battery Positive 3 | — | |
| W5 | SP-14V-1 | M190-B-L | 0.85 | no route | Battery Positive 4 | — | |
| W6 | OEM-1-A | M190-A-38 | 0.85 | no route | Constant +12V | — | |
| W7 | OEM-2-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W8 | OEM-2-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W9 | SP-GND-1 | M190-B-G | 0.85 | no route | Battery Negative 1 | — | |
| W10 | SP-GND-1 | M190-B-W | 0.85 | no route | Battery Negative 2 | — | |
| W11 | SP-GND-1 | M190-B-X | 0.85 | no route | Battery Negative 3 | — | |
| W12 | SP-GND-1 | M190-B-Y | 0.85 | no route | Battery Negative 4 | — | |
| W13 | SP-GND-1 | M190-B-Z | 0.85 | no route | Battery Negative 5 | — | |
| W14 | SP-GND-1 | M190-B-c | 0.85 | no route | Battery Negative 6 | — | |
| W15 | OEM-2-C | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W16 | OEM-2-D | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W17 | SP-0V-1 | M190-A-18 | 0.5 | no route | Sensor 0V C1 | — | |
| W18 | SP-0V-1 | M190-A-19 | 0.5 | no route | Sensor 0V C2 | — | |
| W19 | SP-0V-1 | M190-A-20 | 0.5 | no route | Sensor 0V C3 | — | |
| W20 | SP-0V-1 | M190-C-14 | 0.5 | no route | Sensor 0V A1 | — | |
| W21 | SP-0V-1 | M190-C-15 | 0.5 | no route | Sensor 0V A2 | — | |
| W22 | SP-0V-1 | M190-C-23 | 0.5 | no route | Sensor 0V B1 | — | |
| W23 | SP-0V-1 | M190-C-30 | 0.5 | no route | Sensor 0V B2 | — | |
| W24 | OEM-2-K | M190-A-16 | 0.5 | no route | +5V sensor supply | — | |
| W25 | OEM-2-E | M190-C-18 | 0.5 | no route | Crank position (CAS NE) | — | |
| W26 | OEM-2-G | M190-C-32 | 0.5 | no route | Cam position (CAS G) | — | |
| W27 | OEM-1-G | M190-C-16 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W28 | OEM-1-H | M190-C-8 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W29 | OEM-2-U | M190-A-11 | 0.5 | no route | Injector 1 & 3 (batch) | — | |
| W30 | OEM-2-V | M190-A-3 | 0.5 | no route | Injector 2 & 4 (batch) | — | |
| W31 | OEM-2-Y | M190-B-U | 0.5 | no route | Injector 3 (California sequential) | — | |
| W32 | OEM-2-Z | M190-A-12 | 0.5 | no route | Injector 4 (California sequential) | — | |
| W33 | OEM-1-E | M190-A-2 | 0.5 | no route | Malfunction indicator lamp (MIL) | — | |
| W34 | OEM-2-O | M190-C-42 | 0.5 | no route | Air flow meter (AFM) | — | |
| W35 | OEM-2-N | M190-A-7 | 0.5 | no route | O2 sensor | — | |
| W36 | OEM-2-Q | M190-C-37 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W37 | OEM-2-P | M190-C-39 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W38 | OEM-1-C | M190-A-21 | 0.5 | no route | Start signal | — | |
| W39 | OEM-1-N | M190-A-14 | 0.5 | no route | Wide-open throttle switch | — | |
| W40 | OEM-1-P | M190-A-30 | 0.5 | no route | Power steering pressure switch | — | |
| W41 | OEM-1-Q | M190-A-37 | 0.5 | no route | A/C request | — | |
| W42 | OEM-1-V | M190-C-25 | 0.5 | no route | Neutral/clutch switch | — | |
| W43 | OEM-2-L | M190-C-27 | 0.5 | no route | Idle switch (TPS) | — |
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 (5)
| Severity | Code | Subject | Message |
|---|---|---|---|
| warn | NET_FAMILY | OEM-2-E ↔ M190-C-18 | OEM-2-E "Crank position (CAS NE)" [trigger_in] is wired to M190-C-18 "Universal Digital Input 1" [digital_in]. Hall-type cam/speed signals can use a digital input if it handles the frequency; VR signals cannot. |
| warn | NET_FAMILY | OEM-2-G ↔ M190-C-32 | OEM-2-G "Cam position (CAS G)" [trigger_in] is wired to M190-C-32 "Universal Digital Input 2" [digital_in]. Hall-type cam/speed signals can use a digital input if it handles the frequency; VR signals cannot. |
| warn | NO_FUEL_PUMP | fuel pump | This engine harness has no fuel-pump control path: no fuel-pump relay output is wired to the new ECU. If the stock car switches the pump outside the ECU (an airflow-meter contact or a separate module), the standalone must drive the pump relay itself — see the install notes for this car. |
| info | NET_FAMILY | OEM-1-E ↔ M190-A-2 | OEM-1-E "Malfunction indicator lamp (MIL)" [low_side_out] is wired to M190-A-2 "Low Side Injector 2" [injector_out]. Injector drivers can usually run general low-side loads; check current and PWM frequency. |
| info | UNMAPPED | OEM | 1 optional OEM pins are not mapped: OEM-2-I Tachometer output |
Accepted (0)
| Code | Subject | Reason | By |
|---|
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: - Fuel-pump control: MoTeC M190 needs to drive the fuel pump, but the stock ECU has no fuel-pump output (an airflow-meter contact or a separate module runs it). Add a fuel-pump relay on a spare low-side output — see the install notes for this car. Not wired: - OEM-2 I: Tachometer output: no free tacho/frequency_out/low_side/ls_hs on MoTeC M190
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 | MoTeC: M1 ECU Hardware manual (7 Nov 2013) — M130/M150/M170/M190 pinout tables | https://web.archive.org/web/2023id_/https://www.motec.com.au/hessian/uploads/M1_ECU_Hardware_c2517380e4.pdf | — | 2026-10-05 | 03dc5975f739 |
| 2 | community_copy | 1991 Mazda Miata wiring diagrams (Mitchell reproduction, mellens.net community mirror) | https://trull.org/alex/pubmirror/www.mellens.net/mazda/Mazda-Miata-1991-1993/1991_wiring.pdf | — | 2026-10-08 | 6f957a38ed49 |
| 2 | expert_report | Justin Barrera — Miata NA/NB wiring corrections | — | — | — | — |