MX-5 Miata NA8 1996-97 (BP-ZE, 1.8, OBD-II) → Haltech Nexus S3 HT-213000 (auto)
MX-5 Miata NA8 1996-97 (BP-ZE, 1.8, OBD-II) — Haltech — Nexus S3
Drawn by Michael Gnankou · Rev 0 · proposal · 2026-10-12
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 | 51 wires · 8 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-4-B | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | SP-14V-1 | NEXUSS3-A-18 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-14V-1 | NEXUSS3-A-25 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | OEM-4-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | OEM-4-C | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-4-D | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-4-K | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | SP-GND-1 | NEXUSS3-A-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | SP-GND-1 | NEXUSS3-A-11 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-3-O | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-4-H | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | SP-0V-1 | NEXUSS3-C-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-3-I | NEXUSS3-C-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-4-E | NEXUSS3-C-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | SP-0V-1 | NEXUSS3-C-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-4-G | NEXUSS3-C-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | SP-0V-1 | NEXUSS3-C-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-4-F | NEXUSS3-C-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-4-N | NEXUSS3-A-27 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-4-R | NEXUSS3-A-28 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-4-U | NEXUSS3-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-4-V | NEXUSS3-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-4-W | NEXUSS3-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-4-X | NEXUSS3-A-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-3-B | NEXUSS3-C-10 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-3-F | NEXUSS3-C-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-3-G | NEXUSS3-C-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-1-A | NEXUSS3-A-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-1-B | NEXUSS3-A-9 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-1-G | NEXUSS3-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-1-U | NEXUSS3-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-3-M | NEXUSS3-C-33 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-1-E | NEXUSS3-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-4-J | NEXUSS3-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-4-O | NEXUSS3-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-4-P | NEXUSS3-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-4-Q | NEXUSS3-A-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-4-T | NEXUSS3-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-3-H | NEXUSS3-C-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-3-N | NEXUSS3-C-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W41 | OEM-3-C | NEXUSS3-C-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W42 | OEM-3-D | NEXUSS3-C-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W43 | OEM-3-K | NEXUSS3-C-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W44 | OEM-3-J | NEXUSS3-C-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W45 | OEM-1-M | NEXUSS3-C-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W46 | OEM-1-C | NEXUSS3-C-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W47 | OEM-1-K | NEXUSS3-C-8 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W48 | OEM-1-L | NEXUSS3-C-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W49 | OEM-1-Q | NEXUSS3-C-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W50 | OEM-3-L | NEXUSS3-C-27 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W51 | OEM-3-P | NEXUSS3-C-28 | 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 | NEXUSS3-C-25 | NEXUSS3-A-10 | open (OL) | 5 V sensor reference must not touch power ground | |
| 2 | NEXUSS3-C-25 | NEXUSS3-C-2 | open (OL) | 5 V sensor reference must not touch sensor ground | |
| 3 | NEXUSS3-A-10 | NEXUSS3-A-18 | open (OL) | power ground must not touch +12 V supply | |
| 4 | NEXUSS3-C-2 | NEXUSS3-A-18 | open (OL) | sensor ground must not touch +12 V supply | |
| 5 | NEXUSS3-C-25 | NEXUSS3-A-18 | open (OL) | 5 V sensor reference must not touch +12 V supply |
If any reading doesn't match, stop and get help before powering up.
Revisions
| Rev | Label | By | Date |
|---|---|---|---|
| No revisions yet. | |||
Schematic
Connectors
NEXUSS3-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Injector 1 | — | W21 | — | 0.5 | OEM-4-U | — | — | — |
| 10 | Battery ground | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | Battery ground | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
| 12 | DPO 2 | — | W30 | — | 0.5 | OEM-1-G | — | — | — |
| 13 | Ignition switch input | — | — | — | — | — | — | — | — |
| 14 | DPO 3 | — | W31 | — | 0.5 | OEM-1-U | — | — | — |
| 15 | DPO 4 | — | W33 | — | 0.5 | OEM-1-E | — | — | — |
| 16 | DPO 5 | — | W34 | — | 0.5 | OEM-4-J | — | — | — |
| 17 | DPO 6 | — | W35 | — | 0.5 | OEM-4-O | — | — | — |
| 18 | +12V switched input | — | W2 | — | 0.85 | SP-14V-1 | — | — | — |
| 19 | HBO 1 | — | — | — | — | — | — | — | — |
| 2 | Injector 2 | — | W22 | — | 0.5 | OEM-4-V | — | — | — |
| 20 | HBO 2 | — | — | — | — | — | — | — | — |
| 21 | HBO 3 | — | — | — | — | — | — | — | — |
| 22 | HBO 4 | — | — | — | — | — | — | — | — |
| 23 | CAN 1 High | — | — | — | — | — | — | — | — |
| 24 | CAN 1 Low | — | — | — | — | — | — | — | — |
| 25 | +12V switched input | — | W3 | — | 0.85 | SP-14V-1 | — | — | — |
| 26 | ECR output | — | W28 | — | 0.5 | OEM-1-A | — | — | — |
| 27 | Ignition 1 | — | W19 | — | 0.5 | OEM-4-N | — | — | — |
| 28 | Ignition 2 | — | W20 | — | 0.5 | OEM-4-R | — | — | — |
| 29 | Ignition 3 | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | W23 | — | 0.5 | OEM-4-W | — | — | — |
| 30 | Ignition 4 | — | — | — | — | — | — | — | — |
| 31 | Ignition 5 | — | — | — | — | — | — | — | — |
| 32 | Ignition 6 | — | — | — | — | — | — | — | — |
| 33 | Ignition 7 | — | — | — | — | — | — | — | — |
| 34 | Ignition 8 | — | — | — | — | — | — | — | — |
| 4 | Injector 4 | — | W24 | — | 0.5 | OEM-4-X | — | — | — |
| 5 | Injector 5 | — | W36 | — | 0.5 | OEM-4-P | — | — | — |
| 6 | Injector 6 | — | W37 | — | 0.5 | OEM-4-Q | — | — | — |
| 7 | Injector 7 | — | W38 | — | 0.5 | OEM-4-T | — | — | — |
| 8 | Injector 8 | — | — | — | — | — | — | — | — |
| 9 | DPO 1 | — | W29 | — | 0.5 | OEM-1-B | — | — | — |
NEXUSS3-C
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Trigger + | — | W14 | — | 0.5 | OEM-4-E | — | — | — |
| 10 | AVI 1 | — | W25 | — | 0.5 | OEM-3-B | — | — | — |
| 11 | AVI 2 | — | W26 | — | 0.5 | OEM-3-F | — | — | — |
| 12 | AVI 3 | — | W27 | — | 0.5 | OEM-3-G | — | — | — |
| 13 | AVI 4 | — | W39 | — | 0.5 | OEM-3-H | — | — | — |
| 14 | AVI 5 | — | W40 | — | 0.5 | OEM-3-N | — | — | — |
| 15 | AVI 6 | — | W41 | — | 0.5 | OEM-3-C | — | — | — |
| 16 | AVI 7 | — | W42 | — | 0.5 | OEM-3-D | — | — | — |
| 17 | AVI 8 | — | W43 | — | 0.5 | OEM-3-K | — | — | — |
| 18 | AVI 9 | — | W44 | — | 0.5 | OEM-3-J | — | — | — |
| 19 | SPI 5 | — | W48 | — | 0.5 | OEM-1-L | — | — | — |
| 2 | Trigger - | — | W15 | — | 0.5 | SP-0V-1 | — | — | — |
| 20 | SPI 6 | — | W49 | — | 0.5 | OEM-1-Q | — | — | — |
| 21 | CAN 2 High | — | — | — | — | — | — | — | — |
| 22 | CAN 2 Low | — | — | — | — | — | — | — | — |
| 23 | Knock 1 | — | — | — | — | — | — | — | — |
| 24 | Knock 2 | — | — | — | — | — | — | — | — |
| 25 | +5V | — | W13 | — | 0.5 | OEM-3-I | — | — | — |
| 26 | Signal ground | — | W12 | — | 0.5 | SP-0V-1 | — | — | — |
| 27 | AVI 10 | — | W50 | — | 0.5 | OEM-3-L | — | — | — |
| 28 | AVI 11 | — | W51 | — | 0.5 | OEM-3-P | — | — | — |
| 29 | WBI 1 Heater + | — | — | — | — | — | — | — | — |
| 3 | Home + | — | W16 | — | 0.5 | OEM-4-G | — | — | — |
| 30 | WBI 1 Input | — | — | — | — | — | — | — | — |
| 31 | WBI 1 Pump | — | — | — | — | — | — | — | — |
| 32 | WBI 1 Nernst | — | — | — | — | — | — | — | — |
| 33 | WBI 1 Heater - | — | W32 | — | 0.5 | OEM-3-M | — | — | — |
| 34 | WBI 1 Cal | — | — | — | — | — | — | — | — |
| 4 | Home - | — | W17 | — | 0.5 | SP-0V-1 | — | — | — |
| 5 | SPI 1 | — | W18 | — | 0.5 | OEM-4-F | — | — | — |
| 6 | SPI 2 | — | W45 | — | 0.5 | OEM-1-M | — | — | — |
| 7 | SPI 3 | — | W46 | — | 0.5 | OEM-1-C | — | — | — |
| 8 | SPI 4 | — | W47 | — | 0.5 | OEM-1-K | — | — | — |
| 9 | +8V | — | — | — | — | — | — | — | — |
OEM-1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Cooling fan relay (low-side) | — | W28 | — | 0.5 | NEXUSS3-A-26 | — | — | — |
| B | A/C condenser fan relay | — | W29 | — | 0.5 | NEXUSS3-A-9 | — | — | — |
| C | Starter input (12V while cranking) | — | W46 | — | 0.5 | NEXUSS3-C-7 | — | — | — |
| E | Check engine light (MIL) | — | W33 | — | 0.5 | NEXUSS3-A-15 | — | — | — |
| G | A/C clutch relay | — | W30 | — | 0.5 | NEXUSS3-A-12 | — | — | — |
| K | A/C pressure switch (A/C request) | — | W47 | — | 0.5 | NEXUSS3-C-8 | — | — | — |
| L | Clutch switch | — | W48 | — | 0.5 | NEXUSS3-C-19 | — | — | — |
| M | Vehicle speed sensor (VSS) | — | W45 | — | 0.5 | NEXUSS3-C-6 | — | — | — |
| Q | Brake switch | — | W49 | — | 0.5 | NEXUSS3-C-20 | — | — | — |
| U | Fuel pump relay (low-side) | — | W31 | — | 0.5 | NEXUSS3-A-14 | — | — | — |
OEM-3
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| B | MAF sensor input | — | W25 | — | 0.5 | NEXUSS3-C-10 | — | — | — |
| C | Front O2 sensor input | — | W41 | — | 0.5 | NEXUSS3-C-15 | — | — | — |
| D | Rear O2 sensor input | — | W42 | — | 0.5 | NEXUSS3-C-16 | — | — | — |
| F | Throttle position (TPS) | — | W26 | — | 0.5 | NEXUSS3-C-11 | — | — | — |
| G | Engine coolant temp (CLT) | — | W27 | — | 0.5 | NEXUSS3-C-12 | — | — | — |
| H | EGR boost sensor | — | W39 | — | 0.5 | NEXUSS3-C-13 | — | — | — |
| I | +5V sensor reference | — | W13 | — | 0.5 | NEXUSS3-C-25 | — | — | — |
| J | EGR valve position sensor | — | W44 | — | 0.5 | NEXUSS3-C-18 | — | — | — |
| K | Intake air temp (IAT) | — | W43 | — | 0.5 | NEXUSS3-C-17 | — | — | — |
| L | Idle switch (closed throttle) | — | W50 | — | 0.5 | NEXUSS3-C-27 | — | — | — |
| M | Front O2 heater control | — | W32 | — | 0.5 | NEXUSS3-C-33 | — | — | — |
| N | EGR boost sensor (2nd channel) | — | W40 | — | 0.5 | NEXUSS3-C-14 | — | — | — |
| O | Sensor ground | — | W10 | — | 0.5 | SP-0V-1 | — | — | — |
| P | Power steering pressure switch | — | W51 | — | 0.5 | NEXUSS3-C-28 | — | — | — |
OEM-4
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Chassis ground | — | W4 | — | 0.85 | SP-GND-1 | — | — | — |
| B | ECU power +12V (main relay) | — | W1 | — | 0.85 | SP-14V-1 | — | — | — |
| C | Chassis ground | — | W5 | — | 0.85 | SP-GND-1 | — | — | — |
| D | Chassis ground | — | W6 | — | 0.85 | SP-GND-1 | — | — | — |
| E | Crank position (CKP) sensor | — | W14 | — | 0.5 | NEXUSS3-C-1 | — | — | — |
| F | CAS SGT (cam trigger) | — | W18 | — | 0.5 | NEXUSS3-C-5 | — | — | — |
| G | CAS SGC (cam sync) | — | W16 | — | 0.5 | NEXUSS3-C-3 | — | — | — |
| H | Crank pickup timing ground (CKP gnd) | — | W11 | — | 0.5 | SP-0V-1 | — | — | — |
| I | Permanent +12V (battery) | — | — | — | — | — | — | — | — |
| J | PRC solenoid (FPR control) | — | W34 | — | 0.5 | NEXUSS3-A-16 | — | — | — |
| K | Chassis ground | — | W7 | — | 0.85 | SP-GND-1 | — | — | — |
| L | Tachometer output | — | — | — | — | — | — | — | — |
| N | Ignition coil trigger (cyl 1&4) | — | W19 | — | 0.5 | NEXUSS3-A-27 | — | — | — |
| O | EGR vent solenoid | — | W35 | — | 0.5 | NEXUSS3-A-17 | — | — | — |
| P | EGR vacuum solenoid | — | W36 | — | 0.5 | NEXUSS3-A-5 | — | — | — |
| Q | Idle air control (IAC) valve | — | W37 | — | 0.5 | NEXUSS3-A-6 | — | — | — |
| R | Ignition coil trigger (cyl 2&3) | — | W20 | — | 0.5 | NEXUSS3-A-28 | — | — | — |
| T | EVAP purge solenoid | — | W38 | — | 0.5 | NEXUSS3-A-7 | — | — | — |
| U | Injector 1 (cyl 1) | — | W21 | — | 0.5 | NEXUSS3-A-1 | — | — | — |
| V | Injector 2 (cyl 2) | — | W22 | — | 0.5 | NEXUSS3-A-2 | — | — | — |
| W | Injector 3 (cyl 3) | — | W23 | — | 0.5 | NEXUSS3-A-3 | — | — | — |
| X | Injector 4 (cyl 4) | — | W24 | — | 0.5 | NEXUSS3-A-4 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W10 | — | 0.5 | OEM-3-O | — | — | — |
| 1 | — | — | W11 | — | 0.5 | OEM-4-H | — | — | — |
| 1 | — | — | W12 | — | 0.5 | NEXUSS3-C-26 | — | — | — |
| 1 | — | — | W15 | — | 0.5 | NEXUSS3-C-2 | — | — | — |
| 1 | — | — | W17 | — | 0.5 | NEXUSS3-C-4 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-4-B | — | — | — |
| 1 | — | — | W2 | — | 0.85 | NEXUSS3-A-18 | — | — | — |
| 1 | — | — | W3 | — | 0.85 | NEXUSS3-A-25 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W4 | — | 0.85 | OEM-4-A | — | — | — |
| 1 | — | — | W5 | — | 0.85 | OEM-4-C | — | — | — |
| 1 | — | — | W6 | — | 0.85 | OEM-4-D | — | — | — |
| 1 | — | — | W7 | — | 0.85 | OEM-4-K | — | — | — |
| 1 | — | — | W8 | — | 0.85 | NEXUSS3-A-10 | — | — | — |
| 1 | — | — | W9 | — | 0.85 | NEXUSS3-A-11 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-1-A | Cooling fan relay (low-side) | low_side_out | NEXUSS3-A-26 | ECR output | low_side_out | corroborated | |
| OEM-1-B | A/C condenser fan relay | low_side_out | NEXUSS3-A-9 | DPO 1 | low_side_out | corroborated | |
| OEM-1-C | Starter input (12V while cranking) | digital_in | NEXUSS3-C-7 | SPI 3 | digital_in | corroborated | |
| OEM-1-E | Check engine light (MIL) | low_side_out | NEXUSS3-A-15 | DPO 4 | low_side_out | corroborated | |
| OEM-1-G | A/C clutch relay | low_side_out | NEXUSS3-A-12 | DPO 2 | low_side_out | corroborated | |
| OEM-1-K | A/C pressure switch (A/C request) | digital_in | NEXUSS3-C-8 | SPI 4 | digital_in | corroborated | |
| OEM-1-L | Clutch switch | digital_in | NEXUSS3-C-19 | SPI 5 | digital_in | corroborated | |
| OEM-1-M | Vehicle speed sensor (VSS) | digital_in | NEXUSS3-C-6 | SPI 2 | digital_in | corroborated | |
| OEM-1-Q | Brake switch | digital_in | NEXUSS3-C-20 | SPI 6 | digital_in | corroborated | |
| OEM-1-U | Fuel pump relay (low-side) | low_side_out | NEXUSS3-A-14 | DPO 3 | low_side_out | corroborated | |
| OEM-3-B | MAF sensor input | analog_in | NEXUSS3-C-10 | AVI 1 | analog_in | corroborated | |
| OEM-3-C | Front O2 sensor input | lambda_nb_in | NEXUSS3-C-15 | AVI 6 | analog_in | corroborated | |
| OEM-3-D | Rear O2 sensor input | lambda_nb_in | NEXUSS3-C-16 | AVI 7 | analog_in | corroborated | |
| OEM-3-F | Throttle position (TPS) | analog_in | NEXUSS3-C-11 | AVI 2 | analog_in | corroborated | |
| OEM-3-G | Engine coolant temp (CLT) | temp_in | NEXUSS3-C-12 | AVI 3 | analog_in | corroborated | |
| OEM-3-H | EGR boost sensor | analog_in | NEXUSS3-C-13 | AVI 4 | analog_in | corroborated | |
| OEM-3-I | +5V sensor reference | vref | NEXUSS3-C-25 | +5V | vref | corroborated | |
| OEM-3-J | EGR valve position sensor | analog_in | NEXUSS3-C-18 | AVI 9 | analog_in | corroborated | |
| OEM-3-K | Intake air temp (IAT) | temp_in | NEXUSS3-C-17 | AVI 8 | analog_in | corroborated | |
| OEM-3-L | Idle switch (closed throttle) | digital_in | NEXUSS3-C-27 | AVI 10 | analog_in | corroborated | |
| OEM-3-M | Front O2 heater control | low_side_out | NEXUSS3-C-33 | WBI 1 Heater - | low_side_out | corroborated | |
| OEM-3-N | EGR boost sensor (2nd channel) | analog_in | NEXUSS3-C-14 | AVI 5 | analog_in | corroborated | |
| OEM-3-O | Sensor ground | sensor_ground | NEXUSS3-C-2 + NEXUSS3-C-26 + NEXUSS3-C-4 | Trigger - + Signal ground + Home - | sensor_ground + trigger_in | corroborated | |
| OEM-3-P | Power steering pressure switch | digital_in | NEXUSS3-C-28 | AVI 11 | analog_in | corroborated | |
| OEM-4-A | Chassis ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | corroborated | |
| OEM-4-B | ECU power +12V (main relay) | power_in | NEXUSS3-A-18 + NEXUSS3-A-25 | +12V switched input + +12V switched input | power_in | corroborated | |
| OEM-4-C | Chassis ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | corroborated | |
| OEM-4-D | Chassis ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | corroborated | |
| OEM-4-E | Crank position (CKP) sensor | trigger_in | NEXUSS3-C-1 | Trigger + | trigger_in | corroborated | |
| OEM-4-F | CAS SGT (cam trigger) | trigger_in | NEXUSS3-C-5 | SPI 1 | digital_in | corroborated | |
| OEM-4-G | CAS SGC (cam sync) | trigger_in | NEXUSS3-C-3 | Home + | trigger_in | corroborated | |
| OEM-4-H | Crank pickup timing ground (CKP gnd) | sensor_ground | NEXUSS3-C-2 + NEXUSS3-C-26 + NEXUSS3-C-4 | Trigger - + Signal ground + Home - | sensor_ground + trigger_in | corroborated | |
| OEM-4-I | Permanent +12V (battery) | power_in | — | — | — | corroborated | |
| OEM-4-J | PRC solenoid (FPR control) | low_side_out | NEXUSS3-A-16 | DPO 5 | low_side_out | corroborated | |
| OEM-4-K | Chassis ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | corroborated | |
| OEM-4-L | Tachometer output | tacho_out | — | — | — | corroborated | |
| OEM-4-N | Ignition coil trigger (cyl 1&4) | ignition_out | NEXUSS3-A-27 | Ignition 1 | ignition_out | corroborated | |
| OEM-4-O | EGR vent solenoid | low_side_out | NEXUSS3-A-17 | DPO 6 | low_side_out | corroborated | |
| OEM-4-P | EGR vacuum solenoid | low_side_out | NEXUSS3-A-5 | Injector 5 | injector_out | corroborated | |
| OEM-4-Q | Idle air control (IAC) valve | low_side_out | NEXUSS3-A-6 | Injector 6 | injector_out | corroborated | |
| OEM-4-R | Ignition coil trigger (cyl 2&3) | ignition_out | NEXUSS3-A-28 | Ignition 2 | ignition_out | corroborated | |
| OEM-4-T | EVAP purge solenoid | low_side_out | NEXUSS3-A-7 | Injector 7 | injector_out | corroborated | |
| OEM-4-U | Injector 1 (cyl 1) | injector_out | NEXUSS3-A-1 | Injector 1 | injector_out | corroborated | |
| OEM-4-V | Injector 2 (cyl 2) | injector_out | NEXUSS3-A-2 | Injector 2 | injector_out | corroborated | |
| OEM-4-W | Injector 3 (cyl 3) | injector_out | NEXUSS3-A-3 | Injector 3 | injector_out | corroborated | |
| OEM-4-X | Injector 4 (cyl 4) | injector_out | NEXUSS3-A-4 | Injector 4 | injector_out | corroborated |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-4-B | SP-14V-1 | 0.85 | no route | ECU power +12V (main relay) | — | |
| W2 | SP-14V-1 | NEXUSS3-A-18 | 0.85 | no route | +12V switched input | — | |
| W3 | SP-14V-1 | NEXUSS3-A-25 | 0.85 | no route | +12V switched input | — | |
| W4 | OEM-4-A | SP-GND-1 | 0.85 | no route | Chassis ground | — | |
| W5 | OEM-4-C | SP-GND-1 | 0.85 | no route | Chassis ground | — | |
| W6 | OEM-4-D | SP-GND-1 | 0.85 | no route | Chassis ground | — | |
| W7 | OEM-4-K | SP-GND-1 | 0.85 | no route | Chassis ground | — | |
| W8 | SP-GND-1 | NEXUSS3-A-10 | 0.85 | no route | Battery ground | — | |
| W9 | SP-GND-1 | NEXUSS3-A-11 | 0.85 | no route | Battery ground | — | |
| W10 | OEM-3-O | SP-0V-1 | 0.5 | no route | Sensor ground | — | |
| W11 | OEM-4-H | SP-0V-1 | 0.5 | no route | Crank pickup timing ground (CKP gnd) | — | |
| W12 | SP-0V-1 | NEXUSS3-C-26 | 0.5 | no route | Signal ground | — | |
| W13 | OEM-3-I | NEXUSS3-C-25 | 0.5 | no route | +5V sensor reference | — | |
| W14 | OEM-4-E | NEXUSS3-C-1 | 0.5 | no route | Crank position (CKP) sensor | — | |
| W15 | SP-0V-1 | NEXUSS3-C-2 | 0.5 | no route | Trigger - | — | |
| W16 | OEM-4-G | NEXUSS3-C-3 | 0.5 | no route | CAS SGC (cam sync) | — | |
| W17 | SP-0V-1 | NEXUSS3-C-4 | 0.5 | no route | Home - | — | |
| W18 | OEM-4-F | NEXUSS3-C-5 | 0.5 | no route | CAS SGT (cam trigger) | — | |
| W19 | OEM-4-N | NEXUSS3-A-27 | 0.5 | no route | Ignition coil trigger (cyl 1&4) | — | |
| W20 | OEM-4-R | NEXUSS3-A-28 | 0.5 | no route | Ignition coil trigger (cyl 2&3) | — | |
| W21 | OEM-4-U | NEXUSS3-A-1 | 0.5 | no route | Injector 1 (cyl 1) | — | |
| W22 | OEM-4-V | NEXUSS3-A-2 | 0.5 | no route | Injector 2 (cyl 2) | — | |
| W23 | OEM-4-W | NEXUSS3-A-3 | 0.5 | no route | Injector 3 (cyl 3) | — | |
| W24 | OEM-4-X | NEXUSS3-A-4 | 0.5 | no route | Injector 4 (cyl 4) | — | |
| W25 | OEM-3-B | NEXUSS3-C-10 | 0.5 | no route | MAF sensor input | — | |
| W26 | OEM-3-F | NEXUSS3-C-11 | 0.5 | no route | Throttle position (TPS) | — | |
| W27 | OEM-3-G | NEXUSS3-C-12 | 0.5 | no route | Engine coolant temp (CLT) | — | |
| W28 | OEM-1-A | NEXUSS3-A-26 | 0.5 | no route | Cooling fan relay (low-side) | — | |
| W29 | OEM-1-B | NEXUSS3-A-9 | 0.5 | no route | A/C condenser fan relay | — | |
| W30 | OEM-1-G | NEXUSS3-A-12 | 0.5 | no route | A/C clutch relay | — | |
| W31 | OEM-1-U | NEXUSS3-A-14 | 0.5 | no route | Fuel pump relay (low-side) | — | |
| W32 | OEM-3-M | NEXUSS3-C-33 | 0.5 | no route | Front O2 heater control | — | |
| W33 | OEM-1-E | NEXUSS3-A-15 | 0.5 | no route | Check engine light (MIL) | — | |
| W34 | OEM-4-J | NEXUSS3-A-16 | 0.5 | no route | PRC solenoid (FPR control) | — | |
| W35 | OEM-4-O | NEXUSS3-A-17 | 0.5 | no route | EGR vent solenoid | — | |
| W36 | OEM-4-P | NEXUSS3-A-5 | 0.5 | no route | EGR vacuum solenoid | — | |
| W37 | OEM-4-Q | NEXUSS3-A-6 | 0.5 | no route | Idle air control (IAC) valve | — | |
| W38 | OEM-4-T | NEXUSS3-A-7 | 0.5 | no route | EVAP purge solenoid | — | |
| W39 | OEM-3-H | NEXUSS3-C-13 | 0.5 | no route | EGR boost sensor | — | |
| W40 | OEM-3-N | NEXUSS3-C-14 | 0.5 | no route | EGR boost sensor (2nd channel) | — | |
| W41 | OEM-3-C | NEXUSS3-C-15 | 0.5 | no route | Front O2 sensor input | — | |
| W42 | OEM-3-D | NEXUSS3-C-16 | 0.5 | no route | Rear O2 sensor input | — | |
| W43 | OEM-3-K | NEXUSS3-C-17 | 0.5 | no route | Intake air temp (IAT) | — | |
| W44 | OEM-3-J | NEXUSS3-C-18 | 0.5 | no route | EGR valve position sensor | — | |
| W45 | OEM-1-M | NEXUSS3-C-6 | 0.5 | no route | Vehicle speed sensor (VSS) | — | |
| W46 | OEM-1-C | NEXUSS3-C-7 | 0.5 | no route | Starter input (12V while cranking) | — | |
| W47 | OEM-1-K | NEXUSS3-C-8 | 0.5 | no route | A/C pressure switch (A/C request) | — | |
| W48 | OEM-1-L | NEXUSS3-C-19 | 0.5 | no route | Clutch switch | — | |
| W49 | OEM-1-Q | NEXUSS3-C-20 | 0.5 | no route | Brake switch | — | |
| W50 | OEM-3-L | NEXUSS3-C-27 | 0.5 | no route | Idle switch (closed throttle) | — | |
| W51 | OEM-3-P | NEXUSS3-C-28 | 0.5 | no route | Power steering pressure switch | — |
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 (11)
| Severity | Code | Subject | Message |
|---|---|---|---|
| warn | LOAD_UNKNOWN | NEXUSS3-A-26 | NEXUSS3-A-26 "ECR output" drives OEM-1-A Cooling fan relay (low-side) (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | NET_FAMILY | OEM-3-L ↔ NEXUSS3-C-27 | OEM-3-L "Idle switch (closed throttle)" [digital_in] is wired to NEXUSS3-C-27 "AVI 10" [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-3-P ↔ NEXUSS3-C-28 | OEM-3-P "Power steering pressure switch" [digital_in] is wired to NEXUSS3-C-28 "AVI 11" [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-4-F ↔ NEXUSS3-C-5 | OEM-4-F "CAS SGT (cam trigger)" [trigger_in] is wired to NEXUSS3-C-5 "SPI 1" [digital_in]. Hall-type cam/speed signals can use a digital input if it handles the frequency; VR signals cannot. |
| info | NET_FAMILY | OEM-3-G ↔ NEXUSS3-C-12 | OEM-3-G "Engine coolant temp (CLT)" [temp_in] is wired to NEXUSS3-C-12 "AVI 3" [analog_in]. Thermistor on a plain analog input needs a pull-up; check the channel can enable one. |
| info | NET_FAMILY | OEM-3-K ↔ NEXUSS3-C-17 | OEM-3-K "Intake air temp (IAT)" [temp_in] is wired to NEXUSS3-C-17 "AVI 8" [analog_in]. Thermistor on a plain analog input needs a pull-up; check the channel can enable one. |
| info | NET_FAMILY | OEM-4-H ↔ NEXUSS3-C-4 | OEM-4-H "Crank pickup timing ground (CKP gnd)" [sensor_ground] is wired to NEXUSS3-C-4 "Home -" [trigger_in]. Trigger return tied to sensor/trigger ground: correct for single-ended trigger inputs. |
| info | NET_FAMILY | OEM-4-P ↔ NEXUSS3-A-5 | OEM-4-P "EGR vacuum solenoid" [low_side_out] is wired to NEXUSS3-A-5 "Injector 5" [injector_out]. Injector drivers can usually run general low-side loads; check current and PWM frequency. |
| info | NET_FAMILY | OEM-4-Q ↔ NEXUSS3-A-6 | OEM-4-Q "Idle air control (IAC) valve" [low_side_out] is wired to NEXUSS3-A-6 "Injector 6" [injector_out]. Injector drivers can usually run general low-side loads; check current and PWM frequency. |
| info | NET_FAMILY | OEM-4-T ↔ NEXUSS3-A-7 | OEM-4-T "EVAP purge solenoid" [low_side_out] is wired to NEXUSS3-A-7 "Injector 7" [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-4-L Tachometer output |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-4-I | 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 2026-10-11. Review every wire against both manuals before building. Not wired: - OEM-4 I: Permanent +12V (battery): Haltech Nexus S3 has no battery-constant input; not needed - OEM-4 L: Tachometer output: no free tacho/frequency_out/low_side/ls_hs on Haltech Nexus S3 - NEXUSS3-A 13: Ignition switch input: not fed (the stock ECU has no ignition-sense pin); feed it from a switched-ignition source
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | vendor_doc | AEM EMS 30-1720 Plug-and-Play adapter manual (1996-97 Miata) | https://static.summitracing.com/global/images/instructions/avm-30-1720.pdf | — | — | — |
| 4 | vendor_doc | Haltech: Nexus S3 Plug 'n' Play adapter QSG (Subaru WRX/STI ADM, HT-186300) — ECU Connector A & C pinout | https://www.haltech.com/product/ht-186300-nexus-s3-plug-n-play-adapter-harness/ | archive | 2026-10-05 | 3cab7cd337c2 |
| 4 | vendor_doc | Haltech: Nexus S3/S2 ECU Overview (QSG) — specifications | https://store.haltech.com/product/ht-213000-nexus-s3-ecu-only/ | archive | 2026-10-05 | 388299668207 |
| 3 | community_copy | Mellens.net: 1996 Mazda Miata wiring diagrams (FSM-derived) | http://www.mellens.net/mazda/mazda_miata_extra_manual/1996_wiring.pdf | — | — | — |