MX-5 Miata NA6 1990-93 (B6-ZE, 1.6) → MoTeC M170 13170 (auto)
MX-5 Miata NA6 1990-93 (B6-ZE, 1.6) — MoTeC — M170
⚠ 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 | 36 wires · 6 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 | M170-A-23 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-14V-1 | M170-A-32 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-14V-1 | M170-A-41 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | OEM-1-A | M170-A-54 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-2-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-2-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | SP-GND-1 | M170-A-14 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | SP-GND-1 | M170-A-15 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | SP-GND-1 | M170-A-19 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | SP-GND-1 | M170-A-20 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | SP-GND-1 | M170-A-21 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-2-C | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-2-D | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | SP-0V-1 | M170-A-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | SP-0V-1 | M170-A-27 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-2-K | M170-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-2-E | M170-A-49 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-2-G | M170-A-56 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-1-G | M170-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-1-H | M170-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-2-U | M170-A-33 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-2-V | M170-A-43 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-2-Y | M170-A-50 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-2-Z | M170-A-51 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-1-E | M170-A-63 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-2-O | M170-A-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-2-N | M170-A-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-2-Q | M170-A-28 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-2-P | M170-A-38 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-1-C | M170-A-46 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-1-N | M170-A-45 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-1-P | M170-A-52 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-1-Q | M170-A-53 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-1-V | M170-A-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-2-L | M170-A-22 | 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 | M170-A-23 | M170-A-11 | open (OL) | +12 V supply must not touch sensor ground | |
| 2 | M170-A-23 | M170-A-14 | open (OL) | +12 V supply must not touch power ground | |
| 3 | M170-A-54 | M170-A-11 | open (OL) | +12 V supply must not touch sensor ground | |
| 4 | M170-A-54 | M170-A-14 | open (OL) | +12 V supply must not touch power ground | |
| 5 | M170-A-11 | M170-A-16 | open (OL) | sensor ground must not touch 5 V sensor reference | |
| 6 | M170-A-14 | M170-A-16 | open (OL) | power ground must not touch 5 V sensor reference | |
| 7 | M170-A-23 | M170-A-16 | open (OL) | +12 V supply must not touch 5 V sensor reference | |
| 8 | M170-A-54 | M170-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
M170-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Low Side Ignition 1 | — | W20 | — | 0.5 | OEM-1-G | — | — | — |
| 10 | Low Side Ignition 4 | — | — | — | — | — | — | — | — |
| 11 | Sensor 0V A | — | W15 | — | 0.5 | SP-0V-1 | — | — | — |
| 12 | Analogue Voltage Input 5 | — | — | — | — | — | — | — | — |
| 13 | Universal Digital Input 7 | — | W35 | — | 0.5 | OEM-1-V | — | — | — |
| 14 | Battery Negative 1 | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| 15 | Battery Negative 2 | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
| 16 | Sensor 5.0V A | — | W17 | — | 0.5 | OEM-2-K | — | — | — |
| 17 | Low Side Ignition 5 | — | — | — | — | — | — | — | — |
| 18 | Analogue Voltage Input 2 | — | W28 | — | 0.5 | OEM-2-N | — | — | — |
| 19 | Battery Negative 3 | — | W10 | — | 0.85 | SP-GND-1 | — | — | — |
| 2 | Low Side Ignition 8 | — | — | — | — | — | — | — | — |
| 20 | Battery Negative 4 | — | W11 | — | 0.85 | SP-GND-1 | — | — | — |
| 21 | Battery Negative 5 | — | W12 | — | 0.85 | SP-GND-1 | — | — | — |
| 22 | Universal Digital Input 8 | — | W36 | — | 0.5 | OEM-2-L | — | — | — |
| 23 | Battery Positive | — | W2 | — | 0.85 | SP-14V-1 | — | — | — |
| 24 | Peak Hold Injector 5 | — | — | — | — | — | — | — | — |
| 25 | Low Side Ignition 6 | — | — | — | — | — | — | — | — |
| 26 | Analogue Voltage Input 1 | — | W27 | — | 0.5 | OEM-2-O | — | — | — |
| 27 | Sensor 0V B | — | W16 | — | 0.5 | SP-0V-1 | — | — | — |
| 28 | Analogue Temperature Input 1 | — | W29 | — | 0.5 | OEM-2-Q | — | — | — |
| 29 | Knock Input 1 | — | — | — | — | — | — | — | — |
| 3 | Low Side Ignition 7 | — | — | — | — | — | — | — | — |
| 30 | Analogue Temperature Input 3 | — | — | — | — | — | — | — | — |
| 31 | CAN Bus 1 Low | — | — | — | — | — | — | — | — |
| 32 | Battery Positive | — | W3 | — | 0.85 | SP-14V-1 | — | — | — |
| 33 | Peak Hold Injector 1 | — | W22 | — | 0.5 | OEM-2-U | — | — | — |
| 34 | Sensor 5.0V B | — | — | — | — | — | — | — | — |
| 35 | Analogue Voltage Input 7 | — | — | — | — | — | — | — | — |
| 36 | Analogue Voltage Input 6 | — | — | — | — | — | — | — | — |
| 37 | Sensor 6.3V | — | — | — | — | — | — | — | — |
| 38 | Analogue Temperature Input 2 | — | W30 | — | 0.5 | OEM-2-P | — | — | — |
| 39 | Analogue Temperature Input 4 | — | — | — | — | — | — | — | — |
| 4 | Low Side Ignition 3 | — | — | — | — | — | — | — | — |
| 40 | CAN Bus 1 High | — | — | — | — | — | — | — | — |
| 41 | Battery Positive | — | W4 | — | 0.85 | SP-14V-1 | — | — | — |
| 42 | Peak Hold Injector 6 | — | — | — | — | — | — | — | — |
| 43 | Low Side Injector 1 | — | W23 | — | 0.5 | OEM-2-V | — | — | — |
| 44 | Analogue Voltage Input 8 | — | — | — | — | — | — | — | — |
| 45 | Universal Digital Input 4 | — | W32 | — | 0.5 | OEM-1-N | — | — | — |
| 46 | Universal Digital Input 3 | — | W31 | — | 0.5 | OEM-1-C | — | — | — |
| 47 | Ethernet Transmit - | — | — | — | — | — | — | — | — |
| 48 | Ethernet Transmit + | — | — | — | — | — | — | — | — |
| 49 | Universal Digital Input 1 | — | W18 | — | 0.5 | OEM-2-E | — | — | — |
| 5 | Low Side Ignition 2 | — | W21 | — | 0.5 | OEM-1-H | — | — | — |
| 50 | Peak Hold Injector 2 | — | W24 | — | 0.5 | OEM-2-Y | — | — | — |
| 51 | Low Side Injector 2 | — | W25 | — | 0.5 | OEM-2-Z | — | — | — |
| 52 | Universal Digital Input 5 | — | W33 | — | 0.5 | OEM-1-P | — | — | — |
| 53 | Universal Digital Input 6 | — | W34 | — | 0.5 | OEM-1-Q | — | — | — |
| 54 | Battery Backup | — | W5 | — | 0.85 | OEM-1-A | — | — | — |
| 55 | Ethernet Receive + | — | — | — | — | — | — | — | — |
| 56 | Universal Digital Input 2 | — | W19 | — | 0.5 | OEM-2-G | — | — | — |
| 57 | Peak Hold Injector 7 | — | — | — | — | — | — | — | — |
| 58 | Half Bridge Output 5 | — | — | — | — | — | — | — | — |
| 59 | Half Bridge Output 3 | — | — | — | — | — | — | — | — |
| 6 | Analogue Voltage Input 3 | — | — | — | — | — | — | — | — |
| 60 | Knock Input 2 | — | — | — | — | — | — | — | — |
| 61 | Ethernet Receive - | — | — | — | — | — | — | — | — |
| 62 | Peak Hold Injector 8 | — | — | — | — | — | — | — | — |
| 63 | Peak Hold Injector 3 | — | W26 | — | 0.5 | OEM-1-E | — | — | — |
| 64 | Half Bridge Output 6 | — | — | — | — | — | — | — | — |
| 65 | Half Bridge Output 4 | — | — | — | — | — | — | — | — |
| 66 | Peak Hold Injector 4 | — | — | — | — | — | — | — | — |
| 7 | Analogue Voltage Input 4 | — | — | — | — | — | — | — | — |
| 8 | Half Bridge Output 2 | — | — | — | — | — | — | — | — |
| 9 | Half Bridge Output 1 | — | — | — | — | — | — | — | — |
OEM-1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Constant +12V | — | W5 | — | 0.85 | M170-A-54 | — | — | — |
| B | ECU power +14V (main relay) | — | W1 | — | 0.85 | SP-14V-1 | — | — | — |
| C | Start signal | — | W31 | — | 0.5 | M170-A-46 | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | W26 | — | 0.5 | M170-A-63 | — | — | — |
| G | Ignition 1 (coils 1+4, wasted spark) | — | W20 | — | 0.5 | M170-A-1 | — | — | — |
| H | Ignition 2 (coils 2+3, wasted spark) | — | W21 | — | 0.5 | M170-A-5 | — | — | — |
| N | Wide-open throttle switch | — | W32 | — | 0.5 | M170-A-45 | — | — | — |
| P | Power steering pressure switch | — | W33 | — | 0.5 | M170-A-52 | — | — | — |
| Q | A/C request | — | W34 | — | 0.5 | M170-A-53 | — | — | — |
| V | Neutral/clutch switch | — | W35 | — | 0.5 | M170-A-13 | — | — | — |
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W6 | — | 0.85 | SP-GND-1 | — | — | — |
| B | Power ground | — | W7 | — | 0.85 | SP-GND-1 | — | — | — |
| C | Sensor ground (E2) | — | W13 | — | 0.5 | SP-0V-1 | — | — | — |
| D | Sensor ground (E2) | — | W14 | — | 0.5 | SP-0V-1 | — | — | — |
| E | Crank position (CAS NE) | — | W18 | — | 0.5 | M170-A-49 | — | — | — |
| F | NC | — | — | — | — | — | — | — | — |
| G | Cam position (CAS G) | — | W19 | — | 0.5 | M170-A-56 | — | — | — |
| I | Tachometer output | — | — | — | — | — | — | — | — |
| K | +5V sensor supply | — | W17 | — | 0.5 | M170-A-16 | — | — | — |
| L | Idle switch (TPS) | — | W36 | — | 0.5 | M170-A-22 | — | — | — |
| N | O2 sensor | — | W28 | — | 0.5 | M170-A-18 | — | — | — |
| O | Air flow meter (AFM) | — | W27 | — | 0.5 | M170-A-26 | — | — | — |
| P | Intake air temperature (IAT) | — | W30 | — | 0.5 | M170-A-38 | — | — | — |
| Q | Coolant temperature (ECT) | — | W29 | — | 0.5 | M170-A-28 | — | — | — |
| U | Injector 1 & 3 (batch) | — | W22 | — | 0.5 | M170-A-33 | — | — | — |
| V | Injector 2 & 4 (batch) | — | W23 | — | 0.5 | M170-A-43 | — | — | — |
| Y | Injector 3 (California sequential) | — | W24 | — | 0.5 | M170-A-50 | — | — | — |
| Z | Injector 4 (California sequential) | — | W25 | — | 0.5 | M170-A-51 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W13 | — | 0.5 | OEM-2-C | — | — | — |
| 1 | — | — | W14 | — | 0.5 | OEM-2-D | — | — | — |
| 1 | — | — | W15 | — | 0.5 | M170-A-11 | — | — | — |
| 1 | — | — | W16 | — | 0.5 | M170-A-27 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-1-B | — | — | — |
| 1 | — | — | W2 | — | 0.85 | M170-A-23 | — | — | — |
| 1 | — | — | W3 | — | 0.85 | M170-A-32 | — | — | — |
| 1 | — | — | W4 | — | 0.85 | M170-A-41 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W6 | — | 0.85 | OEM-2-A | — | — | — |
| 1 | — | — | W7 | — | 0.85 | OEM-2-B | — | — | — |
| 1 | — | — | W8 | — | 0.85 | M170-A-14 | — | — | — |
| 1 | — | — | W9 | — | 0.85 | M170-A-15 | — | — | — |
| 1 | — | — | W10 | — | 0.85 | M170-A-19 | — | — | — |
| 1 | — | — | W11 | — | 0.85 | M170-A-20 | — | — | — |
| 1 | — | — | W12 | — | 0.85 | M170-A-21 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-1-A | Constant +12V | power_in | M170-A-54 | Battery Backup | power_in | single_source | |
| OEM-1-B | ECU power +14V (main relay) | power_in | M170-A-23 + M170-A-32 + M170-A-41 | Battery Positive + Battery Positive + Battery Positive | power_in | single_source | |
| OEM-1-C | Start signal | digital_in | M170-A-46 | Universal Digital Input 3 | digital_in | single_source | |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | M170-A-63 | Peak Hold Injector 3 | injector_out | single_source | |
| OEM-1-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | M170-A-1 | Low Side Ignition 1 | ignition_out | single_source | |
| OEM-1-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | M170-A-5 | Low Side Ignition 2 | ignition_out | single_source | |
| OEM-1-N | Wide-open throttle switch | digital_in | M170-A-45 | Universal Digital Input 4 | digital_in | single_source | |
| OEM-1-P | Power steering pressure switch | digital_in | M170-A-52 | Universal Digital Input 5 | digital_in | single_source | |
| OEM-1-Q | A/C request | digital_in | M170-A-53 | Universal Digital Input 6 | digital_in | single_source | |
| OEM-1-V | Neutral/clutch switch | digital_in | M170-A-13 | Universal Digital Input 7 | digital_in | single_source | |
| OEM-2-A | Power ground | ground | M170-A-14 + M170-A-15 + M170-A-19 + M170-A-20 + M170-A-21 | Battery Negative 1 + Battery Negative 2 + Battery Negative 3 + Battery Negative 4 + Battery Negative 5 | ground | single_source | |
| OEM-2-B | Power ground | ground | M170-A-14 + M170-A-15 + M170-A-19 + M170-A-20 + M170-A-21 | Battery Negative 1 + Battery Negative 2 + Battery Negative 3 + Battery Negative 4 + Battery Negative 5 | ground | single_source | |
| OEM-2-C | Sensor ground (E2) | sensor_ground | M170-A-11 + M170-A-27 | Sensor 0V A + Sensor 0V B | sensor_ground | corroborated | |
| OEM-2-D | Sensor ground (E2) | sensor_ground | M170-A-11 + M170-A-27 | Sensor 0V A + Sensor 0V B | sensor_ground | corroborated | |
| OEM-2-E | Crank position (CAS NE) | trigger_in | M170-A-49 | Universal Digital Input 1 | digital_in | single_source | |
| OEM-2-F | NC | — | — | — | — | corroborated | |
| OEM-2-G | Cam position (CAS G) | trigger_in | M170-A-56 | Universal Digital Input 2 | digital_in | single_source | |
| OEM-2-I | Tachometer output | tacho_out | — | — | — | single_source | |
| OEM-2-K | +5V sensor supply | vref | M170-A-16 | Sensor 5.0V A | vref | single_source | |
| OEM-2-L | Idle switch (TPS) | digital_in | M170-A-22 | Universal Digital Input 8 | digital_in | single_source | |
| OEM-2-N | O2 sensor | lambda_nb_in | M170-A-18 | Analogue Voltage Input 2 | analog_in | single_source | |
| OEM-2-O | Air flow meter (AFM) | analog_in | M170-A-26 | Analogue Voltage Input 1 | analog_in | single_source | |
| OEM-2-P | Intake air temperature (IAT) | temp_in | M170-A-38 | Analogue Temperature Input 2 | temp_in | single_source | |
| OEM-2-Q | Coolant temperature (ECT) | temp_in | M170-A-28 | Analogue Temperature Input 1 | temp_in | single_source | |
| OEM-2-U | Injector 1 & 3 (batch) | injector_out | M170-A-33 | Peak Hold Injector 1 | injector_out | corroborated | |
| OEM-2-V | Injector 2 & 4 (batch) | injector_out | M170-A-43 | Low Side Injector 1 | injector_out | corroborated | |
| OEM-2-Y | Injector 3 (California sequential) | injector_out | M170-A-50 | Peak Hold Injector 2 | injector_out | corroborated | |
| OEM-2-Z | Injector 4 (California sequential) | injector_out | M170-A-51 | Low Side 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 | M170-A-23 | 0.85 | no route | Battery Positive | — | |
| W3 | SP-14V-1 | M170-A-32 | 0.85 | no route | Battery Positive | — | |
| W4 | SP-14V-1 | M170-A-41 | 0.85 | no route | Battery Positive | — | |
| W5 | OEM-1-A | M170-A-54 | 0.85 | no route | Constant +12V | — | |
| W6 | OEM-2-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W7 | OEM-2-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W8 | SP-GND-1 | M170-A-14 | 0.85 | no route | Battery Negative 1 | — | |
| W9 | SP-GND-1 | M170-A-15 | 0.85 | no route | Battery Negative 2 | — | |
| W10 | SP-GND-1 | M170-A-19 | 0.85 | no route | Battery Negative 3 | — | |
| W11 | SP-GND-1 | M170-A-20 | 0.85 | no route | Battery Negative 4 | — | |
| W12 | SP-GND-1 | M170-A-21 | 0.85 | no route | Battery Negative 5 | — | |
| W13 | OEM-2-C | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W14 | OEM-2-D | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W15 | SP-0V-1 | M170-A-11 | 0.5 | no route | Sensor 0V A | — | |
| W16 | SP-0V-1 | M170-A-27 | 0.5 | no route | Sensor 0V B | — | |
| W17 | OEM-2-K | M170-A-16 | 0.5 | no route | +5V sensor supply | — | |
| W18 | OEM-2-E | M170-A-49 | 0.5 | no route | Crank position (CAS NE) | — | |
| W19 | OEM-2-G | M170-A-56 | 0.5 | no route | Cam position (CAS G) | — | |
| W20 | OEM-1-G | M170-A-1 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W21 | OEM-1-H | M170-A-5 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W22 | OEM-2-U | M170-A-33 | 0.5 | no route | Injector 1 & 3 (batch) | — | |
| W23 | OEM-2-V | M170-A-43 | 0.5 | no route | Injector 2 & 4 (batch) | — | |
| W24 | OEM-2-Y | M170-A-50 | 0.5 | no route | Injector 3 (California sequential) | — | |
| W25 | OEM-2-Z | M170-A-51 | 0.5 | no route | Injector 4 (California sequential) | — | |
| W26 | OEM-1-E | M170-A-63 | 0.5 | no route | Malfunction indicator lamp (MIL) | — | |
| W27 | OEM-2-O | M170-A-26 | 0.5 | no route | Air flow meter (AFM) | — | |
| W28 | OEM-2-N | M170-A-18 | 0.5 | no route | O2 sensor | — | |
| W29 | OEM-2-Q | M170-A-28 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W30 | OEM-2-P | M170-A-38 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W31 | OEM-1-C | M170-A-46 | 0.5 | no route | Start signal | — | |
| W32 | OEM-1-N | M170-A-45 | 0.5 | no route | Wide-open throttle switch | — | |
| W33 | OEM-1-P | M170-A-52 | 0.5 | no route | Power steering pressure switch | — | |
| W34 | OEM-1-Q | M170-A-53 | 0.5 | no route | A/C request | — | |
| W35 | OEM-1-V | M170-A-13 | 0.5 | no route | Neutral/clutch switch | — | |
| W36 | OEM-2-L | M170-A-22 | 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 ↔ M170-A-49 | OEM-2-E "Crank position (CAS NE)" [trigger_in] is wired to M170-A-49 "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 ↔ M170-A-56 | OEM-2-G "Cam position (CAS G)" [trigger_in] is wired to M170-A-56 "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 ↔ M170-A-63 | OEM-1-E "Malfunction indicator lamp (MIL)" [low_side_out] is wired to M170-A-63 "Peak Hold Injector 3" [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 M170 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 M170
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 | — | — | — | — |