MX-5 Miata NB2 2001-05 (BP-Z3, VVT; excludes Mazdaspeed) → Motorsport Electronics ME221 (auto)
MX-5 Miata NB2 2001-05 (BP-Z3, VVT; excludes Mazdaspeed) — 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.
Install modifications
Steps on the car itself, outside the harness. Every harness for this car inherits them.
- Re-route the pressure-sensor vacuum hose to the intake manifoldrequired
Re-route the pressure sensor's (Mazda "EGR boost sensor", pin 4AE) vacuum hose directly to the intake manifold, bypassing the EGR boost solenoid. The stock ECU multiplexes baro + MAP through that solenoid: with it off the sensor reads atmosphere, with it energized it reads manifold. After re-routing the sensor reads MAP only, so the standalone needs its own barometric source — its onboard baro sensor if fitted, or a separate baro sensor on a spare analog input. (Alternative, not recommended: keep the hose stock and have the ECU energize the solenoid permanently via a low-side output switched with ignition; this costs an output.)
Why: With the solenoid off (its default) the sensor reads atmospheric pressure, not manifold pressure, so a standalone that uses this sensor as its MAP input would read the wrong value.
Where: EGR boost solenoid and the pressure sensor's vacuum hose (sensor signal 4AE).
Source: Justin Barrera — Miata NA/NB wiring corrections
| Status | proposal · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | none |
| Size of the job | 45 wires · 7 connectors · 0 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-P | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-4-AF | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | OEM-4-D | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-14V-1 | ME221-C1-15 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | SP-14V-1 | ME221-C1-64 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-3-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-3-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | OEM-4-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | SP-GND-1 | ME221-C1-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | SP-GND-1 | ME221-C1-61 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | SP-GND-1 | ME221-C1-89 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | SP-GND-1 | ME221-C1-90 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-4-O | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | SP-0V-1 | ME221-C1-52 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | SP-0V-1 | ME221-C1-84 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-4-L | ME221-C1-45 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-3-Y | ME221-C1-81 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-3-V | ME221-C1-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-4-M | ME221-C1-53 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-3-F | ME221-C1-32 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-3-I | ME221-C1-31 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-2-A | ME221-C1-63 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-2-D | ME221-C1-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-2-G | ME221-C1-33 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-2-J | ME221-C1-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-2-B | ME221-C1-73 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-2-C | ME221-C1-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-2-K | ME221-C1-74 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-2-M | ME221-C1-44 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-3-H | ME221-C1-69 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-3-J | ME221-C1-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-3-P | ME221-C1-39 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-2-E | ME221-C1-67 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-2-F | ME221-C1-68 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-2-H | ME221-C1-70 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-2-I | ME221-C1-71 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-3-O | ME221-C1-79 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-4-X | ME221-C1-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-4-AE | ME221-C1-56 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-4-V | ME221-C1-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W41 | OEM-4-AA | ME221-C1-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W42 | OEM-4-P | ME221-C1-86 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W43 | OEM-4-N | ME221-C1-57 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W44 | OEM-3-T | ME221-C1-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W45 | OEM-3-S | ME221-C1-7 | 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): Re-route the pressure-sensor vacuum hose to the intake manifold.
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-C1-45 | ME221-C1-52 | open (OL) | 5 V sensor reference must not touch sensor ground | |
| 4 | ME221-C1-10 | ME221-C1-45 | open (OL) | power ground must not touch 5 V sensor reference | |
| 5 | ME221-C1-15 | ME221-C1-45 | 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
ME221-C1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | COIL 4 | — | — | — | — | — | — | — | — |
| 10 | GROUND CHASSIS | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
| 12 | LOW SIDE 2 | — | W27 | — | 0.5 | OEM-2-C | — | — | — |
| 14 | LSU +12V | — | — | — | — | — | — | — | — |
| 15 | IGN +12V | — | W4 | — | 0.85 | SP-14V-1 | — | — | — |
| 16 | LSU HEATER -VE | — | W31 | — | 0.5 | OEM-3-J | — | — | — |
| 17 | ANA VOLT 3 | — | W40 | — | 0.5 | OEM-4-V | — | — | — |
| 18 | ANA VOLT 4 | — | W41 | — | 0.5 | OEM-4-AA | — | — | — |
| 19 | LSU UN | — | — | — | — | — | — | — | — |
| 2 | COIL 3 | — | — | — | — | — | — | — | — |
| 20 | LSU VM | — | — | — | — | — | — | — | — |
| 21 | CAN 1 HIGH | — | — | — | — | — | — | — | — |
| 22 | CAM A VR+ | — | W18 | — | 0.5 | OEM-3-V | — | — | — |
| 23 | CAM A VR- | — | — | — | — | — | — | — | — |
| 24 | SERIAL 1 GROUND | — | — | — | — | — | — | — | — |
| 25 | SERIAL 1 TX | — | — | — | — | — | — | — | — |
| 26 | ANA VOLT 1 | — | W38 | — | 0.5 | OEM-4-X | — | — | — |
| 3 | INJECTOR 4 | — | W25 | — | 0.5 | OEM-2-J | — | — | — |
| 31 | COIL 2 | — | W21 | — | 0.5 | OEM-3-I | — | — | — |
| 32 | COIL 1 | — | W20 | — | 0.5 | OEM-3-F | — | — | — |
| 33 | INJECTOR 3 | — | W24 | — | 0.5 | OEM-2-G | — | — | — |
| 35 | USB D+ | — | — | — | — | — | — | — | — |
| 36 | USB D- | — | — | — | — | — | — | — | — |
| 37 | LOW SIDE RELAY 11 | — | — | — | — | — | — | — | — |
| 38 | USB VBUS | — | — | — | — | — | — | — | — |
| 39 | LOW SIDE 6 | — | W32 | — | 0.5 | OEM-3-P | — | — | — |
| 4 | INJECTOR 2 | — | W23 | — | 0.5 | OEM-2-D | — | — | — |
| 41 | USB GROUND | — | — | — | — | — | — | — | — |
| 42 | LOW SIDE RELAY 12 | — | — | — | — | — | — | — | — |
| 43 | LOW SIDE RELAY 14 | — | — | — | — | — | — | — | — |
| 44 | LOW SIDE 4 | — | W29 | — | 0.5 | OEM-2-M | — | — | — |
| 45 | 5V REF | — | W16 | — | 0.5 | OEM-4-L | — | — | — |
| 46 | 5V REF | — | — | — | — | — | — | — | — |
| 49 | LSU IA | — | — | — | — | — | — | — | — |
| 50 | LSU IP | — | — | — | — | — | — | — | — |
| 51 | CAN 1 LOW | — | — | — | — | — | — | — | — |
| 52 | SENSORS GROUND | — | W14 | — | 0.5 | SP-0V-1 | — | — | — |
| 53 | KNOCK 1 SIGNAL | — | W19 | — | 0.5 | OEM-4-M | — | — | — |
| 55 | SERIAL 1 RX | — | — | — | — | — | — | — | — |
| 56 | ANA VOLT 2 | — | W39 | — | 0.5 | OEM-4-AE | — | — | — |
| 57 | ANA TEMP 2 | — | W43 | — | 0.5 | OEM-4-N | — | — | — |
| 6 | DIG_IN 1 | — | W44 | — | 0.5 | OEM-3-T | — | — | — |
| 61 | GROUND | — | W10 | — | 0.85 | SP-GND-1 | — | — | — |
| 63 | INJECTOR 1 | — | W22 | — | 0.5 | OEM-2-A | — | — | — |
| 64 | VBAT | — | W5 | — | 0.85 | SP-14V-1 | — | — | — |
| 67 | Stepper 1 / A1 | — | W33 | — | 0.5 | OEM-2-E | — | — | — |
| 68 | Stepper 2 / A2 | — | W34 | — | 0.5 | OEM-2-F | — | — | — |
| 69 | LOW SIDE 5 | — | W30 | — | 0.5 | OEM-3-H | — | — | — |
| 7 | DIG_IN 2 | — | W45 | — | 0.5 | OEM-3-S | — | — | — |
| 70 | Stepper 3 / B1 | — | W35 | — | 0.5 | OEM-2-H | — | — | — |
| 71 | Stepper 4 / B2 | — | W36 | — | 0.5 | OEM-2-I | — | — | — |
| 72 | LOW SIDE RELAY 13 | — | — | — | — | — | — | — | — |
| 73 | LOW SIDE 1 | — | W26 | — | 0.5 | OEM-2-B | — | — | — |
| 74 | LOW SIDE 3 | — | W28 | — | 0.5 | OEM-2-K | — | — | — |
| 76 | 5V REF | — | — | — | — | — | — | — | — |
| 79 | TACHOMETER | — | W37 | — | 0.5 | OEM-3-O | — | — | — |
| 80 | CRANK VR- | — | — | — | — | — | — | — | — |
| 81 | CRANK VR+ | — | W17 | — | 0.5 | OEM-3-Y | — | — | — |
| 84 | Sensor Ground | — | W15 | — | 0.5 | SP-0V-1 | — | — | — |
| 86 | ANA TEMP 1 | — | W42 | — | 0.5 | OEM-4-P | — | — | — |
| 89 | GROUND | — | W11 | — | 0.85 | SP-GND-1 | — | — | — |
| 90 | GROUND | — | W12 | — | 0.85 | SP-GND-1 | — | — | — |
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Injector 1 | — | W22 | — | 0.5 | ME221-C1-63 | — | — | — |
| B | Cooling fan relay | — | W26 | — | 0.5 | ME221-C1-73 | — | — | — |
| C | Condenser fan relay | — | W27 | — | 0.5 | ME221-C1-12 | — | — | — |
| D | Injector 2 | — | W23 | — | 0.5 | ME221-C1-4 | — | — | — |
| E | EGR valve | — | W33 | — | 0.5 | ME221-C1-67 | — | — | — |
| F | EGR valve | — | W34 | — | 0.5 | ME221-C1-68 | — | — | — |
| G | Injector 3 | — | W24 | — | 0.5 | ME221-C1-33 | — | — | — |
| H | EGR valve | — | W35 | — | 0.5 | ME221-C1-70 | — | — | — |
| I | EGR valve | — | W36 | — | 0.5 | ME221-C1-71 | — | — | — |
| J | Injector 4 | — | W25 | — | 0.5 | ME221-C1-3 | — | — | — |
| K | A/C clutch relay | — | W28 | — | 0.5 | ME221-C1-74 | — | — | — |
| M | Fuel pump relay | — | W29 | — | 0.5 | ME221-C1-44 | — | — | — |
| N | VTCS solenoid (intake butterflies) | — | — | — | — | — | — | — | — |
| P | ISC valve +14V feed | — | W1 | — | 0.85 | SP-14V-1 | — | — | — |
| Q | ISC valve low side | — | — | — | — | — | — | — | — |
| R | Malfunction indicator lamp (MIL) | — | — | — | — | — | — | — | — |
OEM-3
| 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 | — | — | — |
| D | EGR boost solenoid | — | — | — | — | — | — | — | — |
| E | Charcoal canister purge | — | — | — | — | — | — | — | — |
| F | Ignition 1 (coils 1+4, wasted spark) | — | W20 | — | 0.5 | ME221-C1-32 | — | — | — |
| H | Main relay | — | W30 | — | 0.5 | ME221-C1-69 | — | — | — |
| I | Ignition 2 (coils 2+3, wasted spark) | — | W21 | — | 0.5 | ME221-C1-31 | — | — | — |
| J | Front O2 heater | — | W31 | — | 0.5 | ME221-C1-16 | — | — | — |
| M | Alternator control | — | — | — | — | — | — | — | — |
| O | Tachometer output | — | W37 | — | 0.5 | ME221-C1-79 | — | — | — |
| P | Rear O2 heater | — | W32 | — | 0.5 | ME221-C1-39 | — | — | — |
| S | Immobiliser | — | W45 | — | 0.5 | ME221-C1-7 | — | — | — |
| T | Vehicle speed | — | W44 | — | 0.5 | ME221-C1-6 | — | — | — |
| U | Charge lamp | — | — | — | — | — | — | — | — |
| V | Cam position (CMP) | — | W18 | — | 0.5 | ME221-C1-22 | — | — | — |
| Y | Crank position (CKP) | — | W17 | — | 0.5 | ME221-C1-81 | — | — | — |
OEM-4
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| AA | Rear O2 signal | — | W41 | — | 0.5 | ME221-C1-18 | — | — | — |
| AD | Fuel level | — | — | — | — | — | — | — | — |
| AE | Pressure sensor (Mazda: EGR boost sensor) | — | W39 | — | 0.5 | ME221-C1-56 | — | — | — |
| AF | ECU power +14V (main relay) | — | W2 | — | 0.85 | SP-14V-1 | — | — | — |
| AG | Constant +12V | — | — | — | — | — | — | — | — |
| B | Brake switch | — | — | — | — | — | — | — | — |
| C | Power steering pressure switch | — | — | — | — | — | — | — | — |
| D | VVT oil-control solenoid +12V feed | — | W3 | — | 0.85 | SP-14V-1 | — | — | — |
| F | A/C request | — | — | — | — | — | — | — | — |
| H | Neutral switch | — | — | — | — | — | — | — | — |
| I | Clutch switch | — | — | — | — | — | — | — | — |
| J | VTCS vacuum switch | — | — | — | — | — | — | — | — |
| L | +5V sensor supply | — | W16 | — | 0.5 | ME221-C1-45 | — | — | — |
| M | Knock sensor | — | W19 | — | 0.5 | ME221-C1-53 | — | — | — |
| N | Intake air temperature (IAT) | — | W43 | — | 0.5 | ME221-C1-57 | — | — | — |
| O | Signal ground | — | W13 | — | 0.5 | SP-0V-1 | — | — | — |
| P | Coolant temperature (ECT) | — | W42 | — | 0.5 | ME221-C1-86 | — | — | — |
| R | VVT oil-control solenoid (low-side control) | — | — | — | — | — | — | — | — |
| V | Throttle position (TPS) | — | W40 | — | 0.5 | ME221-C1-17 | — | — | — |
| W | Front O2 signal | — | — | — | — | — | — | — | — |
| X | Mass air flow (MAF) | — | W38 | — | 0.5 | ME221-C1-26 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W13 | — | 0.5 | OEM-4-O | — | — | — |
| 1 | — | — | W14 | — | 0.5 | ME221-C1-52 | — | — | — |
| 1 | — | — | W15 | — | 0.5 | ME221-C1-84 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-2-P | — | — | — |
| 1 | — | — | W2 | — | 0.85 | OEM-4-AF | — | — | — |
| 1 | — | — | W3 | — | 0.85 | OEM-4-D | — | — | — |
| 1 | — | — | W4 | — | 0.85 | ME221-C1-15 | — | — | — |
| 1 | — | — | W5 | — | 0.85 | ME221-C1-64 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W6 | — | 0.85 | OEM-3-A | — | — | — |
| 1 | — | — | W7 | — | 0.85 | OEM-3-B | — | — | — |
| 1 | — | — | W8 | — | 0.85 | OEM-4-A | — | — | — |
| 1 | — | — | W9 | — | 0.85 | ME221-C1-10 | — | — | — |
| 1 | — | — | W10 | — | 0.85 | ME221-C1-61 | — | — | — |
| 1 | — | — | W11 | — | 0.85 | ME221-C1-89 | — | — | — |
| 1 | — | — | W12 | — | 0.85 | ME221-C1-90 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-2-A | Injector 1 | injector_out | ME221-C1-63 | INJECTOR 1 | injector_out | single_source | |
| OEM-2-B | Cooling fan relay | low_side_out | ME221-C1-73 | LOW SIDE 1 | low_side_out | single_source | |
| OEM-2-C | Condenser fan relay | low_side_out | ME221-C1-12 | LOW SIDE 2 | low_side_out | single_source | |
| OEM-2-D | Injector 2 | injector_out | ME221-C1-4 | INJECTOR 2 | injector_out | single_source | |
| OEM-2-E | EGR valve | low_side_out | ME221-C1-67 | Stepper 1 / A1 | hbridge_out | single_source | |
| OEM-2-F | EGR valve | low_side_out | ME221-C1-68 | Stepper 2 / A2 | hbridge_out | single_source | |
| OEM-2-G | Injector 3 | injector_out | ME221-C1-33 | INJECTOR 3 | injector_out | single_source | |
| OEM-2-H | EGR valve | low_side_out | ME221-C1-70 | Stepper 3 / B1 | hbridge_out | single_source | |
| OEM-2-I | EGR valve | low_side_out | ME221-C1-71 | Stepper 4 / B2 | hbridge_out | single_source | |
| OEM-2-J | Injector 4 | injector_out | ME221-C1-3 | INJECTOR 4 | injector_out | single_source | |
| OEM-2-K | A/C clutch relay | low_side_out | ME221-C1-74 | LOW SIDE 3 | low_side_out | single_source | |
| OEM-2-M | Fuel pump relay | low_side_out | ME221-C1-44 | LOW SIDE 4 | low_side_out | single_source | |
| OEM-2-N | VTCS solenoid (intake butterflies) | low_side_out | — | — | — | single_source | |
| OEM-2-P | ISC valve +14V feed | power_in | ME221-C1-15 + ME221-C1-64 | IGN +12V + VBAT | power_in | single_source | |
| OEM-2-Q | ISC valve low side | low_side_out | — | — | — | single_source | |
| OEM-2-R | Malfunction indicator lamp (MIL) | low_side_out | — | — | — | single_source | |
| OEM-3-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-3-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-3-D | EGR boost solenoid | — | — | — | — | single_source | |
| OEM-3-E | Charcoal canister purge | low_side_out | — | — | — | single_source | |
| OEM-3-F | Ignition 1 (coils 1+4, wasted spark) | ignition_out | ME221-C1-32 | COIL 1 | ignition_out | single_source | |
| OEM-3-H | Main relay | low_side_out | ME221-C1-69 | LOW SIDE 5 | low_side_out | single_source | |
| OEM-3-I | Ignition 2 (coils 2+3, wasted spark) | ignition_out | ME221-C1-31 | COIL 2 | ignition_out | single_source | |
| OEM-3-J | Front O2 heater | low_side_out | ME221-C1-16 | LSU HEATER -VE | low_side_out | single_source | |
| OEM-3-M | Alternator control | low_side_out | — | — | — | single_source | |
| OEM-3-O | Tachometer output | tacho_out | ME221-C1-79 | TACHOMETER | tacho_out | single_source | |
| OEM-3-P | Rear O2 heater | low_side_out | ME221-C1-39 | LOW SIDE 6 | low_side_out | single_source | |
| OEM-3-S | Immobiliser | digital_in | ME221-C1-7 | DIG_IN 2 | digital_in | single_source | |
| OEM-3-T | Vehicle speed | digital_in | ME221-C1-6 | DIG_IN 1 | digital_in | single_source | |
| OEM-3-U | Charge lamp | low_side_out | — | — | — | single_source | |
| OEM-3-V | Cam position (CMP) | trigger_in | ME221-C1-22 | CAM A VR+ | trigger_in | single_source | |
| OEM-3-Y | Crank position (CKP) | trigger_in | ME221-C1-81 | CRANK VR+ | trigger_in | single_source | |
| OEM-4-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-4-AA | Rear O2 signal | lambda_nb_in | ME221-C1-18 | ANA VOLT 4 | analog_in | single_source | |
| OEM-4-AD | Fuel level | analog_in | — | — | — | single_source | |
| OEM-4-AE | Pressure sensor (Mazda: EGR boost sensor) | analog_in | ME221-C1-56 | ANA VOLT 2 | analog_in | corroborated | |
| OEM-4-AF | ECU power +14V (main relay) | power_in | ME221-C1-15 + ME221-C1-64 | IGN +12V + VBAT | power_in | single_source | |
| OEM-4-AG | Constant +12V | power_in | — | — | — | single_source | |
| OEM-4-B | Brake switch | digital_in | — | — | — | single_source | |
| OEM-4-C | Power steering pressure switch | digital_in | — | — | — | single_source | |
| OEM-4-D | VVT oil-control solenoid +12V feed | power_in | ME221-C1-15 + ME221-C1-64 | IGN +12V + VBAT | power_in | Y | single_source |
| OEM-4-F | A/C request | digital_in | — | — | — | single_source | |
| OEM-4-H | Neutral switch | digital_in | — | — | — | single_source | |
| OEM-4-I | Clutch switch | digital_in | — | — | — | single_source | |
| OEM-4-J | VTCS vacuum switch | digital_in | — | — | — | single_source | |
| OEM-4-L | +5V sensor supply | vref | ME221-C1-45 | 5V REF | vref | single_source | |
| OEM-4-M | Knock sensor | knock_in | ME221-C1-53 | KNOCK 1 SIGNAL | knock_in | single_source | |
| OEM-4-N | Intake air temperature (IAT) | temp_in | ME221-C1-57 | ANA TEMP 2 | temp_in | single_source | |
| OEM-4-O | Signal ground | sensor_ground | ME221-C1-52 + ME221-C1-84 | SENSORS GROUND + Sensor Ground | sensor_ground | single_source | |
| OEM-4-P | Coolant temperature (ECT) | temp_in | ME221-C1-86 | ANA TEMP 1 | temp_in | single_source | |
| OEM-4-R | VVT oil-control solenoid (low-side control) | low_side_out | — | — | — | VY | corroborated |
| OEM-4-V | Throttle position (TPS) | analog_in | ME221-C1-17 | ANA VOLT 3 | analog_in | single_source | |
| OEM-4-W | Front O2 signal | lambda_nb_in | — | — | — | single_source | |
| OEM-4-X | Mass air flow (MAF) | analog_in | ME221-C1-26 | ANA VOLT 1 | analog_in | single_source |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-2-P | SP-14V-1 | 0.85 | no route | ISC valve +14V feed | — | |
| W2 | OEM-4-AF | SP-14V-1 | 0.85 | no route | ECU power +14V (main relay) | — | |
| W3 | OEM-4-D | SP-14V-1 | 0.85 | no route | VVT oil-control solenoid +12V feed | — | |
| W4 | SP-14V-1 | ME221-C1-15 | 0.85 | no route | IGN +12V | — | |
| W5 | SP-14V-1 | ME221-C1-64 | 0.85 | no route | VBAT | — | |
| W6 | OEM-3-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W7 | OEM-3-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W8 | OEM-4-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W9 | SP-GND-1 | ME221-C1-10 | 0.85 | no route | GROUND CHASSIS | — | |
| W10 | SP-GND-1 | ME221-C1-61 | 0.85 | no route | GROUND | — | |
| W11 | SP-GND-1 | ME221-C1-89 | 0.85 | no route | GROUND | — | |
| W12 | SP-GND-1 | ME221-C1-90 | 0.85 | no route | GROUND | — | |
| W13 | OEM-4-O | SP-0V-1 | 0.5 | no route | Signal ground | — | |
| W14 | SP-0V-1 | ME221-C1-52 | 0.5 | no route | SENSORS GROUND | — | |
| W15 | SP-0V-1 | ME221-C1-84 | 0.5 | no route | Sensor Ground | — | |
| W16 | OEM-4-L | ME221-C1-45 | 0.5 | no route | +5V sensor supply | — | |
| W17 | OEM-3-Y | ME221-C1-81 | 0.5 | no route | Crank position (CKP) | — | |
| W18 | OEM-3-V | ME221-C1-22 | 0.5 | no route | Cam position (CMP) | — | |
| W19 | OEM-4-M | ME221-C1-53 | 0.5 | no route | Knock sensor | — | |
| W20 | OEM-3-F | ME221-C1-32 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W21 | OEM-3-I | ME221-C1-31 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W22 | OEM-2-A | ME221-C1-63 | 0.5 | no route | Injector 1 | — | |
| W23 | OEM-2-D | ME221-C1-4 | 0.5 | no route | Injector 2 | — | |
| W24 | OEM-2-G | ME221-C1-33 | 0.5 | no route | Injector 3 | — | |
| W25 | OEM-2-J | ME221-C1-3 | 0.5 | no route | Injector 4 | — | |
| W26 | OEM-2-B | ME221-C1-73 | 0.5 | no route | Cooling fan relay | — | |
| W27 | OEM-2-C | ME221-C1-12 | 0.5 | no route | Condenser fan relay | — | |
| W28 | OEM-2-K | ME221-C1-74 | 0.5 | no route | A/C clutch relay | — | |
| W29 | OEM-2-M | ME221-C1-44 | 0.5 | no route | Fuel pump relay | — | |
| W30 | OEM-3-H | ME221-C1-69 | 0.5 | no route | Main relay | — | |
| W31 | OEM-3-J | ME221-C1-16 | 0.5 | no route | Front O2 heater | — | |
| W32 | OEM-3-P | ME221-C1-39 | 0.5 | no route | Rear O2 heater | — | |
| W33 | OEM-2-E | ME221-C1-67 | 0.5 | no route | EGR valve | — | |
| W34 | OEM-2-F | ME221-C1-68 | 0.5 | no route | EGR valve | — | |
| W35 | OEM-2-H | ME221-C1-70 | 0.5 | no route | EGR valve | — | |
| W36 | OEM-2-I | ME221-C1-71 | 0.5 | no route | EGR valve | — | |
| W37 | OEM-3-O | ME221-C1-79 | 0.5 | no route | Tachometer output | — | |
| W38 | OEM-4-X | ME221-C1-26 | 0.5 | no route | Mass air flow (MAF) | — | |
| W39 | OEM-4-AE | ME221-C1-56 | 0.5 | no route | Pressure sensor (Mazda: EGR boost sensor) | — | |
| W40 | OEM-4-V | ME221-C1-17 | 0.5 | no route | Throttle position (TPS) | — | |
| W41 | OEM-4-AA | ME221-C1-18 | 0.5 | no route | Rear O2 signal | — | |
| W42 | OEM-4-P | ME221-C1-86 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W43 | OEM-4-N | ME221-C1-57 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W44 | OEM-3-T | ME221-C1-6 | 0.5 | no route | Vehicle speed | — | |
| W45 | OEM-3-S | ME221-C1-7 | 0.5 | no route | Immobiliser | — |
Bill of materials
| Category | Part number | Manufacturer | Description | Qty | Unit |
|---|
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 ↔ ME221-C1-67 | OEM-2-E "EGR valve" [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-F ↔ ME221-C1-68 | OEM-2-F "EGR valve" [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. |
| warn | NET_FAMILY | OEM-2-H ↔ ME221-C1-70 | OEM-2-H "EGR valve" [low_side_out] is wired to ME221-C1-70 "Stepper 3 / B1" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-2-I ↔ ME221-C1-71 | OEM-2-I "EGR valve" [low_side_out] is wired to ME221-C1-71 "Stepper 4 / B2" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| info | UNMAPPED | OEM | 16 optional OEM pins are not mapped: OEM-2-N VTCS solenoid (intake butterflies); OEM-2-Q ISC valve low side; OEM-2-R Malfunction indicator lamp (MIL); OEM-3-D EGR boost solenoid; OEM-3-E Charcoal canister purge; OEM-3-M Alternator control; OEM-3-U Charge lamp; OEM-4-AD Fuel level; OEM-4-B Brake switch; OEM-4-C Power steering pressure switch; OEM-4-F A/C request; OEM-4-H Neutral switch; OEM-4-I Clutch switch; OEM-4-J VTCS vacuum switch; OEM-4-R VVT oil-control solenoid (low-side control); OEM-4-W Front O2 signal |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-4-AG | 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-4 AG: Constant +12V: Motorsport Electronics ME221 has no battery-constant input; not needed - OEM-2 Q: ISC valve low side: no free low_side/ls_hs/injector/hbridge rated ≥ 1.0 A on Motorsport Electronics ME221 - OEM-2 N: VTCS solenoid (intake butterflies): no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-2 R: Malfunction indicator lamp (MIL): no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 E: Charcoal canister purge: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 M: Alternator control: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 U: Charge lamp: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-4 R: VVT oil-control solenoid (low-side control): no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-4 W: Front O2 signal: no free o2_narrowband/analog_0_5 on Motorsport Electronics ME221 - OEM-4 AD: Fuel level: no free analog_0_5 on Motorsport Electronics ME221 - OEM-4 B: Brake switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-4 C: Power steering pressure switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-4 F: A/C request: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-4 H: Neutral switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-4 I: Clutch switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-4 J: VTCS vacuum switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-3 D: EGR boost solenoid: not classified in the library; wire by hand
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | vendor_doc | Adaptronic eSel039 Select Plugin ECU for Mazda MX5 / Miata NB8B/C (OEM ECU pinout) | https://www.miataturbo.net/attachments/ecus-tuning-54/04-msm-ecu-pinout-104032/nb8bc_oem_ecu_pinouts-224948d1602912806 | — | — | — |
| 4 | vendor_doc | Link G4X MX5NB2X install manual (NB2 2001-05) | https://linkecu.com/documentation/MX5XNB2.pdf | archive | 2026-10-05 | 741efdd9f2c8 |
| 4 | oem_manual | Mazda MX-5 NB2 (2003) wiring diagram — engine / starting / charging | https://web.archive.org/web/20191104195207/http://mellens.net/mazda/mazda_miata_extra_manual/2003_wiring.pdf | — | 2026-10-05 | 5ee0777f12c1 |
| 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 | — | — | — | — |