MX-5 Miata NA8 1994-97 (BP-ZE, 1.8) → Motorsport Electronics ME221 (auto)
MX-5 Miata NA8 1994-95 (BP-ZE, 1.8, OBD-I) — Motorsport Electronics — ME221
Drawn by Michael Gnankou · Rev 0 · proposal · 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.
| Status | proposal · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | none |
| Size of the job | 40 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 | ME221-C1-15 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-14V-1 | ME221-C1-64 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | OEM-2-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | OEM-2-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | SP-GND-1 | ME221-C1-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | SP-GND-1 | ME221-C1-61 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | SP-GND-1 | ME221-C1-89 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | SP-GND-1 | ME221-C1-90 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-2-C | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-2-D | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | OEM-2-F | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | SP-0V-1 | ME221-C1-52 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | SP-0V-1 | ME221-C1-84 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-2-K | ME221-C1-45 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-2-E | ME221-C1-81 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-2-G | ME221-C1-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-1-G | ME221-C1-32 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-1-H | ME221-C1-31 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-2-U | ME221-C1-63 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-2-V | ME221-C1-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-2-Y | ME221-C1-33 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-2-Z | ME221-C1-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-1-J | ME221-C1-73 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-1-R | ME221-C1-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-2-S | ME221-C1-74 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-2-T | ME221-C1-44 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-2-W | ME221-C1-69 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-1-E | ME221-C1-39 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-2-R | ME221-C1-67 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-2-X | ME221-C1-68 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-2-I | ME221-C1-79 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-2-O | ME221-C1-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-2-M | ME221-C1-56 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-2-N | ME221-C1-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-2-Q | ME221-C1-86 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-2-P | ME221-C1-57 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-1-M | ME221-C1-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-1-C | ME221-C1-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-1-P | ME221-C1-18 | 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 | ME221-C1-15 | ME221-C1-10 | open (OL) | +12 V supply must not touch power ground | |
| 2 | ME221-C1-15 | ME221-C1-52 | open (OL) | +12 V supply must not touch sensor ground | |
| 3 | ME221-C1-10 | ME221-C1-45 | open (OL) | power ground must not touch 5 V sensor reference | |
| 4 | ME221-C1-15 | ME221-C1-45 | open (OL) | +12 V supply must not touch 5 V sensor reference | |
| 5 | ME221-C1-52 | ME221-C1-45 | 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
ME221-C1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | COIL 4 | — | — | — | — | — | — | — | — |
| 10 | GROUND CHASSIS | — | W6 | — | 0.85 | SP-GND-1 | — | — | — |
| 12 | LOW SIDE 2 | — | W25 | — | 0.5 | OEM-1-R | — | — | — |
| 14 | LSU +12V | — | — | — | — | — | — | — | — |
| 15 | IGN +12V | — | W2 | — | 0.85 | SP-14V-1 | — | — | — |
| 16 | LSU HEATER -VE | — | — | — | — | — | — | — | — |
| 17 | ANA VOLT 3 | — | W35 | — | 0.5 | OEM-2-N | — | — | — |
| 18 | ANA VOLT 4 | — | W40 | — | 0.5 | OEM-1-P | — | — | — |
| 19 | LSU UN | — | — | — | — | — | — | — | — |
| 2 | COIL 3 | — | — | — | — | — | — | — | — |
| 20 | LSU VM | — | — | — | — | — | — | — | — |
| 21 | CAN 1 HIGH | — | — | — | — | — | — | — | — |
| 22 | CAM A VR+ | — | W17 | — | 0.5 | OEM-2-G | — | — | — |
| 23 | CAM A VR- | — | — | — | — | — | — | — | — |
| 24 | SERIAL 1 GROUND | — | — | — | — | — | — | — | — |
| 25 | SERIAL 1 TX | — | — | — | — | — | — | — | — |
| 26 | ANA VOLT 1 | — | W33 | — | 0.5 | OEM-2-O | — | — | — |
| 3 | INJECTOR 4 | — | W23 | — | 0.5 | OEM-2-Z | — | — | — |
| 31 | COIL 2 | — | W19 | — | 0.5 | OEM-1-H | — | — | — |
| 32 | COIL 1 | — | W18 | — | 0.5 | OEM-1-G | — | — | — |
| 33 | INJECTOR 3 | — | W22 | — | 0.5 | OEM-2-Y | — | — | — |
| 35 | USB D+ | — | — | — | — | — | — | — | — |
| 36 | USB D- | — | — | — | — | — | — | — | — |
| 37 | LOW SIDE RELAY 11 | — | — | — | — | — | — | — | — |
| 38 | USB VBUS | — | — | — | — | — | — | — | — |
| 39 | LOW SIDE 6 | — | W29 | — | 0.5 | OEM-1-E | — | — | — |
| 4 | INJECTOR 2 | — | W21 | — | 0.5 | OEM-2-V | — | — | — |
| 41 | USB GROUND | — | — | — | — | — | — | — | — |
| 42 | LOW SIDE RELAY 12 | — | — | — | — | — | — | — | — |
| 43 | LOW SIDE RELAY 14 | — | — | — | — | — | — | — | — |
| 44 | LOW SIDE 4 | — | W27 | — | 0.5 | OEM-2-T | — | — | — |
| 45 | 5V REF | — | W15 | — | 0.5 | OEM-2-K | — | — | — |
| 46 | 5V REF | — | — | — | — | — | — | — | — |
| 49 | LSU IA | — | — | — | — | — | — | — | — |
| 50 | LSU IP | — | — | — | — | — | — | — | — |
| 51 | CAN 1 LOW | — | — | — | — | — | — | — | — |
| 52 | SENSORS GROUND | — | W13 | — | 0.5 | SP-0V-1 | — | — | — |
| 53 | KNOCK 1 SIGNAL | — | — | — | — | — | — | — | — |
| 55 | SERIAL 1 RX | — | — | — | — | — | — | — | — |
| 56 | ANA VOLT 2 | — | W34 | — | 0.5 | OEM-2-M | — | — | — |
| 57 | ANA TEMP 2 | — | W37 | — | 0.5 | OEM-2-P | — | — | — |
| 6 | DIG_IN 1 | — | W38 | — | 0.5 | OEM-1-M | — | — | — |
| 61 | GROUND | — | W7 | — | 0.85 | SP-GND-1 | — | — | — |
| 63 | INJECTOR 1 | — | W20 | — | 0.5 | OEM-2-U | — | — | — |
| 64 | VBAT | — | W3 | — | 0.85 | SP-14V-1 | — | — | — |
| 67 | Stepper 1 / A1 | — | W30 | — | 0.5 | OEM-2-R | — | — | — |
| 68 | Stepper 2 / A2 | — | W31 | — | 0.5 | OEM-2-X | — | — | — |
| 69 | LOW SIDE 5 | — | W28 | — | 0.5 | OEM-2-W | — | — | — |
| 7 | DIG_IN 2 | — | W39 | — | 0.5 | OEM-1-C | — | — | — |
| 70 | Stepper 3 / B1 | — | — | — | — | — | — | — | — |
| 71 | Stepper 4 / B2 | — | — | — | — | — | — | — | — |
| 72 | LOW SIDE RELAY 13 | — | — | — | — | — | — | — | — |
| 73 | LOW SIDE 1 | — | W24 | — | 0.5 | OEM-1-J | — | — | — |
| 74 | LOW SIDE 3 | — | W26 | — | 0.5 | OEM-2-S | — | — | — |
| 76 | 5V REF | — | — | — | — | — | — | — | — |
| 79 | TACHOMETER | — | W32 | — | 0.5 | OEM-2-I | — | — | — |
| 80 | CRANK VR- | — | — | — | — | — | — | — | — |
| 81 | CRANK VR+ | — | W16 | — | 0.5 | OEM-2-E | — | — | — |
| 84 | Sensor Ground | — | W14 | — | 0.5 | SP-0V-1 | — | — | — |
| 86 | ANA TEMP 1 | — | W36 | — | 0.5 | OEM-2-Q | — | — | — |
| 89 | GROUND | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| 90 | GROUND | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
OEM-1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Constant +12V | — | — | — | — | — | — | — | — |
| B | ECU power +14V (main relay) | — | W1 | — | 0.85 | SP-14V-1 | — | — | — |
| C | Start signal | — | W39 | — | 0.5 | ME221-C1-7 | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | W29 | — | 0.5 | ME221-C1-39 | — | — | — |
| G | Ignition 1 (coils 1+4, wasted spark) | — | W18 | — | 0.5 | ME221-C1-32 | — | — | — |
| H | Ignition 2 (coils 2+3, wasted spark) | — | W19 | — | 0.5 | ME221-C1-31 | — | — | — |
| J | A/C relay | — | W24 | — | 0.5 | ME221-C1-73 | — | — | — |
| M | Vehicle speed | — | W38 | — | 0.5 | ME221-C1-6 | — | — | — |
| P | Power steering pressure switch | — | W40 | — | 0.5 | ME221-C1-18 | — | — | — |
| Q | A/C request | — | — | — | — | — | — | — | — |
| R | Cooling fan relay | — | W25 | — | 0.5 | ME221-C1-12 | — | — | — |
| V | Neutral/clutch switch | — | — | — | — | — | — | — | — |
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W4 | — | 0.85 | SP-GND-1 | — | — | — |
| B | Power ground | — | W5 | — | 0.85 | SP-GND-1 | — | — | — |
| C | Sensor ground (E2) | — | W10 | — | 0.5 | SP-0V-1 | — | — | — |
| D | Sensor ground (E2) | — | W11 | — | 0.5 | SP-0V-1 | — | — | — |
| E | Crank position (CAS NE) | — | W16 | — | 0.5 | ME221-C1-81 | — | — | — |
| F | MAF ground | — | W12 | — | 0.5 | SP-0V-1 | — | — | — |
| G | Cam position (CAS G) | — | W17 | — | 0.5 | ME221-C1-22 | — | — | — |
| I | Tachometer output | — | W32 | — | 0.5 | ME221-C1-79 | — | — | — |
| K | +5V sensor supply | — | W15 | — | 0.5 | ME221-C1-45 | — | — | — |
| M | Throttle position (TPS) | — | W34 | — | 0.5 | ME221-C1-56 | — | — | — |
| N | O2 sensor | — | W35 | — | 0.5 | ME221-C1-17 | — | — | — |
| O | Mass air flow (MAF) | — | W33 | — | 0.5 | ME221-C1-26 | — | — | — |
| P | Intake air temperature (IAT) | — | W37 | — | 0.5 | ME221-C1-57 | — | — | — |
| Q | Coolant temperature (ECT) | — | W36 | — | 0.5 | ME221-C1-86 | — | — | — |
| R | PRC solenoid (fuel pressure regulator) | — | W30 | — | 0.5 | ME221-C1-67 | — | — | — |
| S | Condenser fan relay | — | W26 | — | 0.5 | ME221-C1-74 | — | — | — |
| T | Fuel pump relay | — | W27 | — | 0.5 | ME221-C1-44 | — | — | — |
| U | Injector 1 | — | W20 | — | 0.5 | ME221-C1-63 | — | — | — |
| V | Injector 2 | — | W21 | — | 0.5 | ME221-C1-4 | — | — | — |
| W | ISC solenoid | — | W28 | — | 0.5 | ME221-C1-69 | — | — | — |
| X | Evap purge solenoid | — | W31 | — | 0.5 | ME221-C1-68 | — | — | — |
| Y | Injector 3 | — | W22 | — | 0.5 | ME221-C1-33 | — | — | — |
| Z | Injector 4 | — | W23 | — | 0.5 | ME221-C1-3 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W10 | — | 0.5 | OEM-2-C | — | — | — |
| 1 | — | — | W11 | — | 0.5 | OEM-2-D | — | — | — |
| 1 | — | — | W12 | — | 0.5 | OEM-2-F | — | — | — |
| 1 | — | — | W13 | — | 0.5 | ME221-C1-52 | — | — | — |
| 1 | — | — | W14 | — | 0.5 | ME221-C1-84 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-1-B | — | — | — |
| 1 | — | — | W2 | — | 0.85 | ME221-C1-15 | — | — | — |
| 1 | — | — | W3 | — | 0.85 | ME221-C1-64 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W4 | — | 0.85 | OEM-2-A | — | — | — |
| 1 | — | — | W5 | — | 0.85 | OEM-2-B | — | — | — |
| 1 | — | — | W6 | — | 0.85 | ME221-C1-10 | — | — | — |
| 1 | — | — | W7 | — | 0.85 | ME221-C1-61 | — | — | — |
| 1 | — | — | W8 | — | 0.85 | ME221-C1-89 | — | — | — |
| 1 | — | — | W9 | — | 0.85 | ME221-C1-90 | — | — | — |
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 | ME221-C1-15 + ME221-C1-64 | IGN +12V + VBAT | power_in | single_source | |
| OEM-1-C | Start signal | digital_in | ME221-C1-7 | DIG_IN 2 | digital_in | single_source | |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | ME221-C1-39 | LOW SIDE 6 | low_side_out | single_source | |
| OEM-1-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | ME221-C1-32 | COIL 1 | ignition_out | single_source | |
| OEM-1-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | ME221-C1-31 | COIL 2 | ignition_out | single_source | |
| OEM-1-J | A/C relay | low_side_out | ME221-C1-73 | LOW SIDE 1 | low_side_out | single_source | |
| OEM-1-M | Vehicle speed | digital_in | ME221-C1-6 | DIG_IN 1 | digital_in | single_source | |
| OEM-1-P | Power steering pressure switch | digital_in | ME221-C1-18 | ANA VOLT 4 | analog_in | single_source | |
| OEM-1-Q | A/C request | digital_in | — | — | — | single_source | |
| OEM-1-R | Cooling fan relay | low_side_out | ME221-C1-12 | LOW SIDE 2 | low_side_out | single_source | |
| OEM-1-V | Neutral/clutch switch | digital_in | — | — | — | single_source | |
| OEM-2-A | Power ground | ground | ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90 | GROUND CHASSIS + GROUND + GROUND + GROUND | ground | single_source | |
| OEM-2-B | Power ground | ground | ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90 | GROUND CHASSIS + GROUND + GROUND + GROUND | ground | single_source | |
| OEM-2-C | Sensor ground (E2) | sensor_ground | ME221-C1-52 + ME221-C1-84 | SENSORS GROUND + Sensor Ground | sensor_ground | corroborated | |
| OEM-2-D | Sensor ground (E2) | sensor_ground | ME221-C1-52 + ME221-C1-84 | SENSORS GROUND + Sensor Ground | sensor_ground | corroborated | |
| OEM-2-E | Crank position (CAS NE) | trigger_in | ME221-C1-81 | CRANK VR+ | trigger_in | single_source | |
| OEM-2-F | MAF ground | sensor_ground | ME221-C1-52 + ME221-C1-84 | SENSORS GROUND + Sensor Ground | sensor_ground | single_source | |
| OEM-2-G | Cam position (CAS G) | trigger_in | ME221-C1-22 | CAM A VR+ | trigger_in | single_source | |
| OEM-2-I | Tachometer output | tacho_out | ME221-C1-79 | TACHOMETER | tacho_out | single_source | |
| OEM-2-K | +5V sensor supply | vref | ME221-C1-45 | 5V REF | vref | single_source | |
| OEM-2-M | Throttle position (TPS) | analog_in | ME221-C1-56 | ANA VOLT 2 | analog_in | single_source | |
| OEM-2-N | O2 sensor | lambda_nb_in | ME221-C1-17 | ANA VOLT 3 | analog_in | single_source | |
| OEM-2-O | Mass air flow (MAF) | analog_in | ME221-C1-26 | ANA VOLT 1 | analog_in | single_source | |
| OEM-2-P | Intake air temperature (IAT) | temp_in | ME221-C1-57 | ANA TEMP 2 | temp_in | single_source | |
| OEM-2-Q | Coolant temperature (ECT) | temp_in | ME221-C1-86 | ANA TEMP 1 | temp_in | single_source | |
| OEM-2-R | PRC solenoid (fuel pressure regulator) | low_side_out | ME221-C1-67 | Stepper 1 / A1 | hbridge_out | single_source | |
| OEM-2-S | Condenser fan relay | low_side_out | ME221-C1-74 | LOW SIDE 3 | low_side_out | single_source | |
| OEM-2-T | Fuel pump relay | low_side_out | ME221-C1-44 | LOW SIDE 4 | low_side_out | single_source | |
| OEM-2-U | Injector 1 | injector_out | ME221-C1-63 | INJECTOR 1 | injector_out | single_source | |
| OEM-2-V | Injector 2 | injector_out | ME221-C1-4 | INJECTOR 2 | injector_out | single_source | |
| OEM-2-W | ISC solenoid | low_side_out | ME221-C1-69 | LOW SIDE 5 | low_side_out | single_source | |
| OEM-2-X | Evap purge solenoid | low_side_out | ME221-C1-68 | Stepper 2 / A2 | hbridge_out | single_source | |
| OEM-2-Y | Injector 3 | injector_out | ME221-C1-33 | INJECTOR 3 | injector_out | single_source | |
| OEM-2-Z | Injector 4 | injector_out | ME221-C1-3 | INJECTOR 4 | injector_out | single_source |
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 | ME221-C1-15 | 0.85 | no route | IGN +12V | — | |
| W3 | SP-14V-1 | ME221-C1-64 | 0.85 | no route | VBAT | — | |
| W4 | OEM-2-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W5 | OEM-2-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W6 | SP-GND-1 | ME221-C1-10 | 0.85 | no route | GROUND CHASSIS | — | |
| W7 | SP-GND-1 | ME221-C1-61 | 0.85 | no route | GROUND | — | |
| W8 | SP-GND-1 | ME221-C1-89 | 0.85 | no route | GROUND | — | |
| W9 | SP-GND-1 | ME221-C1-90 | 0.85 | no route | GROUND | — | |
| W10 | OEM-2-C | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W11 | OEM-2-D | SP-0V-1 | 0.5 | no route | Sensor ground (E2) | — | |
| W12 | OEM-2-F | SP-0V-1 | 0.5 | no route | MAF ground | — | |
| W13 | SP-0V-1 | ME221-C1-52 | 0.5 | no route | SENSORS GROUND | — | |
| W14 | SP-0V-1 | ME221-C1-84 | 0.5 | no route | Sensor Ground | — | |
| W15 | OEM-2-K | ME221-C1-45 | 0.5 | no route | +5V sensor supply | — | |
| W16 | OEM-2-E | ME221-C1-81 | 0.5 | no route | Crank position (CAS NE) | — | |
| W17 | OEM-2-G | ME221-C1-22 | 0.5 | no route | Cam position (CAS G) | — | |
| W18 | OEM-1-G | ME221-C1-32 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W19 | OEM-1-H | ME221-C1-31 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W20 | OEM-2-U | ME221-C1-63 | 0.5 | no route | Injector 1 | — | |
| W21 | OEM-2-V | ME221-C1-4 | 0.5 | no route | Injector 2 | — | |
| W22 | OEM-2-Y | ME221-C1-33 | 0.5 | no route | Injector 3 | — | |
| W23 | OEM-2-Z | ME221-C1-3 | 0.5 | no route | Injector 4 | — | |
| W24 | OEM-1-J | ME221-C1-73 | 0.5 | no route | A/C relay | — | |
| W25 | OEM-1-R | ME221-C1-12 | 0.5 | no route | Cooling fan relay | — | |
| W26 | OEM-2-S | ME221-C1-74 | 0.5 | no route | Condenser fan relay | — | |
| W27 | OEM-2-T | ME221-C1-44 | 0.5 | no route | Fuel pump relay | — | |
| W28 | OEM-2-W | ME221-C1-69 | 0.5 | no route | ISC solenoid | — | |
| W29 | OEM-1-E | ME221-C1-39 | 0.5 | no route | Malfunction indicator lamp (MIL) | — | |
| W30 | OEM-2-R | ME221-C1-67 | 0.5 | no route | PRC solenoid (fuel pressure regulator) | — | |
| W31 | OEM-2-X | ME221-C1-68 | 0.5 | no route | Evap purge solenoid | — | |
| W32 | OEM-2-I | ME221-C1-79 | 0.5 | no route | Tachometer output | — | |
| W33 | OEM-2-O | ME221-C1-26 | 0.5 | no route | Mass air flow (MAF) | — | |
| W34 | OEM-2-M | ME221-C1-56 | 0.5 | no route | Throttle position (TPS) | — | |
| W35 | OEM-2-N | ME221-C1-17 | 0.5 | no route | O2 sensor | — | |
| W36 | OEM-2-Q | ME221-C1-86 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W37 | OEM-2-P | ME221-C1-57 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W38 | OEM-1-M | ME221-C1-6 | 0.5 | no route | Vehicle speed | — | |
| W39 | OEM-1-C | ME221-C1-7 | 0.5 | no route | Start signal | — | |
| W40 | OEM-1-P | ME221-C1-18 | 0.5 | no route | Power steering pressure 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 (4)
| Severity | Code | Subject | Message |
|---|---|---|---|
| warn | NET_FAMILY | OEM-1-P ↔ ME221-C1-18 | OEM-1-P "Power steering pressure switch" [digital_in] is wired to ME221-C1-18 "ANA VOLT 4" [analog_in]. Analog and digital on one net. A switch on an analog input works with a pull-up and a threshold; an analog sensor on a digital input loses its value. |
| warn | NET_FAMILY | OEM-2-R ↔ ME221-C1-67 | OEM-2-R "PRC solenoid (fuel pressure regulator)" [low_side_out] is wired to ME221-C1-67 "Stepper 1 / A1" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-2-X ↔ ME221-C1-68 | OEM-2-X "Evap purge solenoid" [low_side_out] is wired to ME221-C1-68 "Stepper 2 / A2" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| info | UNMAPPED | OEM | 2 optional OEM pins are not mapped: OEM-1-Q A/C request; OEM-1-V Neutral/clutch switch |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-1-A | Battery-constant (memory) feed of the stock ECU: the new ECU has no such input, so it is not needed. | mapping-proposal |
Notes
Auto-mapped by auto_map() from the library pin data on 2026-10-09. Review every wire against both manuals before building. Not wired: - OEM-1 A: Constant +12V: Motorsport Electronics ME221 has no battery-constant input; not needed - OEM-1 Q: A/C request: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-1 V: Neutral/clutch switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221
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 | Motorsport Electronics GEN2 ME221/ME360/ME442 wire-in pinout | https://motorsport-electronics.co.uk/onlinehelp/html/ME442ME360ME221GEN2Wire-InPinout.html | — | — | — |
| 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 |