MX-5 Miata NB1 1999-00 (BP-4W) → Haltech Nexus S3 HT-213000 (auto)
MX-5 Miata NB1 1999-00 (BP-4W) — Haltech — Nexus S3
Drawn by Michael Gnankou · Rev 0 · proposal · 2026-10-08
Before you start
| Status | proposal · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | none |
| Size of the job | 54 wires · 8 connectors · 3 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 | OEM-3-M | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-14V-1 | NEXUSS3-A-18 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-14V-1 | NEXUSS3-A-25 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | OEM-3-A | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-3-B | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-3-C | 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-F | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | SP-0V-1 | NEXUSS3-C-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | OEM-2-I | NEXUSS3-C-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-2-J | NEXUSS3-C-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | SP-0V-1 | NEXUSS3-C-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-2-H | NEXUSS3-C-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | SP-0V-1 | NEXUSS3-C-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-2-F | NEXUSS3-C-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-3-G | NEXUSS3-A-27 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-3-H | NEXUSS3-A-28 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-3-W | NEXUSS3-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-3-X | NEXUSS3-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-3-Y | NEXUSS3-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-3-Z | NEXUSS3-A-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-1-I | NEXUSS3-A-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-1-R | NEXUSS3-A-9 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-1-S | NEXUSS3-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-3-N | NEXUSS3-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-1-U | NEXUSS3-C-33 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-3-V | NEXUSS3-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-3-O | NEXUSS3-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-1-E | NEXUSS3-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-1-O | NEXUSS3-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-1-Q | NEXUSS3-A-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-2-M | NEXUSS3-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-2-N | NEXUSS3-A-8 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-2-O | NEXUSS3-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-2-P | NEXUSS3-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-3-L | NEXUSS3-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-3-Q | NEXUSS3-A-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-2-L | NEXUSS3-C-10 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W41 | OEM-3-E | NEXUSS3-C-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W42 | OEM-2-C | NEXUSS3-C-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W43 | OEM-3-J | NEXUSS3-C-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W44 | OEM-2-E | NEXUSS3-C-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W45 | OEM-2-B | NEXUSS3-C-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W46 | OEM-2-A | NEXUSS3-C-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W47 | OEM-3-K | NEXUSS3-C-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W48 | OEM-3-S | NEXUSS3-C-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W49 | OEM-2-D | NEXUSS3-C-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W50 | OEM-1-F | NEXUSS3-C-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W51 | OEM-1-G | NEXUSS3-C-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W52 | OEM-1-P | NEXUSS3-C-8 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W53 | OEM-1-V | NEXUSS3-C-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W54 | OEM-3-I | NEXUSS3-C-20 | 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-A-18 | NEXUSS3-A-10 | open (OL) | +12 V supply must not touch power ground | |
| 2 | NEXUSS3-A-18 | NEXUSS3-C-2 | open (OL) | +12 V supply must not touch sensor ground | |
| 3 | NEXUSS3-C-25 | NEXUSS3-A-10 | open (OL) | 5 V sensor reference must not touch power ground | |
| 4 | NEXUSS3-C-25 | NEXUSS3-C-2 | open (OL) | 5 V sensor reference must not touch sensor ground | |
| 5 | NEXUSS3-A-18 | NEXUSS3-C-25 | open (OL) | +12 V supply must not touch 5 V sensor reference |
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 | — | W20 | — | 0.5 | OEM-3-W | — | — | — |
| 10 | Battery ground | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | Battery ground | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
| 12 | DPO 2 | — | W26 | — | 0.5 | OEM-1-S | — | — | — |
| 13 | Ignition switch input | — | — | — | — | — | — | — | — |
| 14 | DPO 3 | — | W27 | — | 0.5 | OEM-3-N | — | — | — |
| 15 | DPO 4 | — | W29 | — | 0.5 | OEM-3-V | — | — | — |
| 16 | DPO 5 | — | W30 | — | 0.5 | OEM-3-O | — | — | — |
| 17 | DPO 6 | — | W31 | — | 0.5 | OEM-1-E | — | — | — |
| 18 | +12V switched input | — | W3 | — | 0.85 | SP-14V-1 | — | — | — |
| 19 | HBO 1 | — | W36 | — | 0.5 | OEM-2-O | — | — | — |
| 2 | Injector 2 | — | W21 | — | 0.5 | OEM-3-X | — | — | — |
| 20 | HBO 2 | — | W37 | — | 0.5 | OEM-2-P | — | — | — |
| 21 | HBO 3 | — | W38 | — | 0.5 | OEM-3-L | — | — | — |
| 22 | HBO 4 | — | W39 | — | 0.5 | OEM-3-Q | — | — | — |
| 23 | CAN 1 High | — | — | — | — | — | — | — | — |
| 24 | CAN 1 Low | — | — | — | — | — | — | — | — |
| 25 | +12V switched input | — | W4 | — | 0.85 | SP-14V-1 | — | — | — |
| 26 | ECR output | — | W24 | — | 0.5 | OEM-1-I | — | — | — |
| 27 | Ignition 1 | — | W18 | — | 0.5 | OEM-3-G | — | — | — |
| 28 | Ignition 2 | — | W19 | — | 0.5 | OEM-3-H | — | — | — |
| 29 | Ignition 3 | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | W22 | — | 0.5 | OEM-3-Y | — | — | — |
| 30 | Ignition 4 | — | — | — | — | — | — | — | — |
| 31 | Ignition 5 | — | — | — | — | — | — | — | — |
| 32 | Ignition 6 | — | — | — | — | — | — | — | — |
| 33 | Ignition 7 | — | — | — | — | — | — | — | — |
| 34 | Ignition 8 | — | — | — | — | — | — | — | — |
| 4 | Injector 4 | — | W23 | — | 0.5 | OEM-3-Z | — | — | — |
| 5 | Injector 5 | — | W32 | — | 0.5 | OEM-1-O | — | — | — |
| 6 | Injector 6 | — | W33 | — | 0.5 | OEM-1-Q | — | — | — |
| 7 | Injector 7 | — | W34 | — | 0.5 | OEM-2-M | — | — | — |
| 8 | Injector 8 | — | W35 | — | 0.5 | OEM-2-N | — | — | — |
| 9 | DPO 1 | — | W25 | — | 0.5 | OEM-1-R | — | — | — |
NEXUSS3-C
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Trigger + | — | W13 | — | 0.5 | OEM-2-J | — | — | — |
| 10 | AVI 1 | — | W40 | — | 0.5 | OEM-2-L | — | — | — |
| 11 | AVI 2 | — | W41 | — | 0.5 | OEM-3-E | — | — | — |
| 12 | AVI 3 | — | W42 | — | 0.5 | OEM-2-C | — | — | — |
| 13 | AVI 4 | — | W43 | — | 0.5 | OEM-3-J | — | — | — |
| 14 | AVI 5 | — | W44 | — | 0.5 | OEM-2-E | — | — | — |
| 15 | AVI 6 | — | W45 | — | 0.5 | OEM-2-B | — | — | — |
| 16 | AVI 7 | — | W46 | — | 0.5 | OEM-2-A | — | — | — |
| 17 | AVI 8 | — | W47 | — | 0.5 | OEM-3-K | — | — | — |
| 18 | AVI 9 | — | W48 | — | 0.5 | OEM-3-S | — | — | — |
| 19 | SPI 5 | — | W53 | — | 0.5 | OEM-1-V | — | — | — |
| 2 | Trigger - | — | W14 | — | 0.5 | SP-0V-1 | — | — | — |
| 20 | SPI 6 | — | W54 | — | 0.5 | OEM-3-I | — | — | — |
| 21 | CAN 2 High | — | — | — | — | — | — | — | — |
| 22 | CAN 2 Low | — | — | — | — | — | — | — | — |
| 23 | Knock 1 | — | W17 | — | 0.5 | OEM-2-F | — | — | — |
| 24 | Knock 2 | — | — | — | — | — | — | — | — |
| 25 | +5V | — | W12 | — | 0.5 | OEM-2-I | — | — | — |
| 26 | Signal ground | — | W11 | — | 0.5 | SP-0V-1 | — | — | — |
| 27 | AVI 10 | — | — | — | — | — | — | — | — |
| 28 | AVI 11 | — | — | — | — | — | — | — | — |
| 29 | WBI 1 Heater + | — | — | — | — | — | — | — | — |
| 3 | Home + | — | W15 | — | 0.5 | OEM-2-H | — | — | — |
| 30 | WBI 1 Input | — | — | — | — | — | — | — | — |
| 31 | WBI 1 Pump | — | — | — | — | — | — | — | — |
| 32 | WBI 1 Nernst | — | — | — | — | — | — | — | — |
| 33 | WBI 1 Heater - | — | W28 | — | 0.5 | OEM-1-U | — | — | — |
| 34 | WBI 1 Cal | — | — | — | — | — | — | — | — |
| 4 | Home - | — | W16 | — | 0.5 | SP-0V-1 | — | — | — |
| 5 | SPI 1 | — | W49 | — | 0.5 | OEM-2-D | — | — | — |
| 6 | SPI 2 | — | W50 | — | 0.5 | OEM-1-F | — | — | — |
| 7 | SPI 3 | — | W51 | — | 0.5 | OEM-1-G | — | — | — |
| 8 | SPI 4 | — | W52 | — | 0.5 | OEM-1-P | — | — | — |
| 9 | +8V | — | — | — | — | — | — | — | — |
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 | — | — | — |
| E | Malfunction indicator lamp (MIL) | — | W31 | — | 0.5 | NEXUSS3-A-17 | — | — | — |
| F | Brake switch | — | W50 | — | 0.5 | NEXUSS3-C-6 | — | — | — |
| G | Power steering pressure switch | — | W51 | — | 0.5 | NEXUSS3-C-7 | — | — | — |
| I | Condenser fan relay | — | W24 | — | 0.5 | NEXUSS3-A-26 | — | — | — |
| O | Alternator control | — | W32 | — | 0.5 | NEXUSS3-A-5 | — | — | — |
| P | A/C request | — | W52 | — | 0.5 | NEXUSS3-C-8 | — | — | — |
| Q | Charge lamp | — | W33 | — | 0.5 | NEXUSS3-A-6 | — | — | — |
| R | Cooling fan relay | — | W25 | — | 0.5 | NEXUSS3-A-9 | — | — | — |
| S | A/C clutch relay | — | W26 | — | 0.5 | NEXUSS3-A-12 | — | — | — |
| U | Front O2 heater | — | W28 | — | 0.5 | NEXUSS3-C-33 | — | — | — |
| V | Neutral switch | — | W53 | — | 0.5 | NEXUSS3-C-19 | — | — | — |
OEM-2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Fuel tank pressure | — | W46 | — | 0.5 | NEXUSS3-C-16 | — | — | — |
| B | Intake air temperature (IAT) | — | W45 | — | 0.5 | NEXUSS3-C-15 | — | — | — |
| C | Front O2 signal | — | W42 | — | 0.5 | NEXUSS3-C-12 | — | — | — |
| D | Vehicle speed | — | W49 | — | 0.5 | NEXUSS3-C-5 | — | — | — |
| E | Coolant temperature (ECT) | — | W44 | — | 0.5 | NEXUSS3-C-14 | — | — | — |
| F | Knock sensor | — | W17 | — | 0.5 | NEXUSS3-C-23 | — | — | — |
| H | Cam position (CMP) | — | W15 | — | 0.5 | NEXUSS3-C-3 | — | — | — |
| I | +5V sensor supply | — | W12 | — | 0.5 | NEXUSS3-C-25 | — | — | — |
| J | Crank position (CKP) | — | W13 | — | 0.5 | NEXUSS3-C-1 | — | — | — |
| K | Tachometer output | — | — | — | — | — | — | — | — |
| L | Mass air flow (MAF) | — | W40 | — | 0.5 | NEXUSS3-C-10 | — | — | — |
| M | EGR valve | — | W34 | — | 0.5 | NEXUSS3-A-7 | — | — | — |
| N | EGR valve | — | W35 | — | 0.5 | NEXUSS3-A-8 | — | — | — |
| O | EGR valve | — | W36 | — | 0.5 | NEXUSS3-A-19 | — | — | — |
| P | EGR valve | — | W37 | — | 0.5 | NEXUSS3-A-20 | — | — | — |
OEM-3
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| A | Power ground | — | W5 | — | 0.85 | SP-GND-1 | — | — | — |
| B | Power ground | — | W6 | — | 0.85 | SP-GND-1 | — | — | — |
| C | Power ground | — | W7 | — | 0.85 | SP-GND-1 | — | — | — |
| E | Throttle position (TPS) | — | W41 | — | 0.5 | NEXUSS3-C-11 | — | — | — |
| F | Signal ground | — | W10 | — | 0.5 | SP-0V-1 | — | — | — |
| G | Ignition 1 (coils 1+4, wasted spark) | — | W18 | — | 0.5 | NEXUSS3-A-27 | — | — | — |
| H | Ignition 2 (coils 2+3, wasted spark) | — | W19 | — | 0.5 | NEXUSS3-A-28 | — | — | — |
| I | Clutch switch | — | W54 | — | 0.5 | NEXUSS3-C-20 | — | — | — |
| J | Rear O2 signal | — | W43 | — | 0.5 | NEXUSS3-C-13 | — | — | — |
| K | Fuel level | — | W47 | — | 0.5 | NEXUSS3-C-17 | — | — | — |
| L | Evap purge solenoid | — | W38 | — | 0.5 | NEXUSS3-A-21 | — | — | — |
| M | ISC valve +14V feed | — | W2 | — | 0.85 | SP-14V-1 | — | — | — |
| N | Fuel pump relay | — | W27 | — | 0.5 | NEXUSS3-A-14 | — | — | — |
| O | ISC valve low side | — | W30 | — | 0.5 | NEXUSS3-A-16 | — | — | — |
| Q | VICS solenoid (intake butterflies) | — | W39 | — | 0.5 | NEXUSS3-A-22 | — | — | — |
| S | EGR boost sensor | — | W48 | — | 0.5 | NEXUSS3-C-18 | — | — | — |
| T | EGR boost solenoid | — | — | — | — | — | — | — | — |
| U | Canister drain cut valve (CDCV) | — | — | — | — | — | — | — | — |
| V | Rear O2 heater | — | W29 | — | 0.5 | NEXUSS3-A-15 | — | — | — |
| W | Injector 1 | — | W20 | — | 0.5 | NEXUSS3-A-1 | — | — | — |
| X | Injector 2 | — | W21 | — | 0.5 | NEXUSS3-A-2 | — | — | — |
| Y | Injector 3 | — | W22 | — | 0.5 | NEXUSS3-A-3 | — | — | — |
| Z | Injector 4 | — | W23 | — | 0.5 | NEXUSS3-A-4 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W10 | — | 0.5 | OEM-3-F | — | — | — |
| 1 | — | — | W11 | — | 0.5 | NEXUSS3-C-26 | — | — | — |
| 1 | — | — | W14 | — | 0.5 | NEXUSS3-C-2 | — | — | — |
| 1 | — | — | W16 | — | 0.5 | NEXUSS3-C-4 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-1-B | — | — | — |
| 1 | — | — | W2 | — | 0.85 | OEM-3-M | — | — | — |
| 1 | — | — | W3 | — | 0.85 | NEXUSS3-A-18 | — | — | — |
| 1 | — | — | W4 | — | 0.85 | NEXUSS3-A-25 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W5 | — | 0.85 | OEM-3-A | — | — | — |
| 1 | — | — | W6 | — | 0.85 | OEM-3-B | — | — | — |
| 1 | — | — | W7 | — | 0.85 | OEM-3-C | — | — | — |
| 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 | Constant +12V | power_in | — | — | — | single_source | |
| OEM-1-B | ECU power +14V (main relay) | power_in | NEXUSS3-A-18 + NEXUSS3-A-25 | +12V switched input + +12V switched input | power_in | single_source | |
| OEM-1-E | Malfunction indicator lamp (MIL) | low_side_out | NEXUSS3-A-17 | DPO 6 | low_side_out | single_source | |
| OEM-1-F | Brake switch | digital_in | NEXUSS3-C-6 | SPI 2 | digital_in | single_source | |
| OEM-1-G | Power steering pressure switch | digital_in | NEXUSS3-C-7 | SPI 3 | digital_in | single_source | |
| OEM-1-I | Condenser fan relay | low_side_out | NEXUSS3-A-26 | ECR output | low_side_out | single_source | |
| OEM-1-O | Alternator control | low_side_out | NEXUSS3-A-5 | Injector 5 | injector_out | single_source | |
| OEM-1-P | A/C request | digital_in | NEXUSS3-C-8 | SPI 4 | digital_in | single_source | |
| OEM-1-Q | Charge lamp | low_side_out | NEXUSS3-A-6 | Injector 6 | injector_out | single_source | |
| OEM-1-R | Cooling fan relay | low_side_out | NEXUSS3-A-9 | DPO 1 | low_side_out | single_source | |
| OEM-1-S | A/C clutch relay | low_side_out | NEXUSS3-A-12 | DPO 2 | low_side_out | single_source | |
| OEM-1-U | Front O2 heater | low_side_out | NEXUSS3-C-33 | WBI 1 Heater - | low_side_out | single_source | |
| OEM-1-V | Neutral switch | digital_in | NEXUSS3-C-19 | SPI 5 | digital_in | single_source | |
| OEM-2-A | Fuel tank pressure | analog_in | NEXUSS3-C-16 | AVI 7 | analog_in | single_source | |
| OEM-2-B | Intake air temperature (IAT) | temp_in | NEXUSS3-C-15 | AVI 6 | analog_in | single_source | |
| OEM-2-C | Front O2 signal | lambda_nb_in | NEXUSS3-C-12 | AVI 3 | analog_in | single_source | |
| OEM-2-D | Vehicle speed | digital_in | NEXUSS3-C-5 | SPI 1 | digital_in | single_source | |
| OEM-2-E | Coolant temperature (ECT) | temp_in | NEXUSS3-C-14 | AVI 5 | analog_in | single_source | |
| OEM-2-F | Knock sensor | knock_in | NEXUSS3-C-23 | Knock 1 | knock_in | single_source | |
| OEM-2-H | Cam position (CMP) | trigger_in | NEXUSS3-C-3 | Home + | trigger_in | single_source | |
| OEM-2-I | +5V sensor supply | vref | NEXUSS3-C-25 | +5V | vref | single_source | |
| OEM-2-J | Crank position (CKP) | trigger_in | NEXUSS3-C-1 | Trigger + | trigger_in | single_source | |
| OEM-2-K | Tachometer output | tacho_out | — | — | — | single_source | |
| OEM-2-L | Mass air flow (MAF) | analog_in | NEXUSS3-C-10 | AVI 1 | analog_in | single_source | |
| OEM-2-M | EGR valve | low_side_out | NEXUSS3-A-7 | Injector 7 | injector_out | single_source | |
| OEM-2-N | EGR valve | low_side_out | NEXUSS3-A-8 | Injector 8 | injector_out | single_source | |
| OEM-2-O | EGR valve | low_side_out | NEXUSS3-A-19 | HBO 1 | hbridge_out | single_source | |
| OEM-2-P | EGR valve | low_side_out | NEXUSS3-A-20 | HBO 2 | hbridge_out | single_source | |
| OEM-3-A | Power ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | single_source | |
| OEM-3-B | Power ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | single_source | |
| OEM-3-C | Power ground | ground | NEXUSS3-A-10 + NEXUSS3-A-11 | Battery ground + Battery ground | ground | single_source | |
| OEM-3-E | Throttle position (TPS) | analog_in | NEXUSS3-C-11 | AVI 2 | analog_in | single_source | |
| OEM-3-F | Signal ground | sensor_ground | NEXUSS3-C-2 + NEXUSS3-C-26 + NEXUSS3-C-4 | Trigger - + Signal ground + Home - | sensor_ground + trigger_in | single_source | |
| OEM-3-G | Ignition 1 (coils 1+4, wasted spark) | ignition_out | NEXUSS3-A-27 | Ignition 1 | ignition_out | single_source | |
| OEM-3-H | Ignition 2 (coils 2+3, wasted spark) | ignition_out | NEXUSS3-A-28 | Ignition 2 | ignition_out | single_source | |
| OEM-3-I | Clutch switch | digital_in | NEXUSS3-C-20 | SPI 6 | digital_in | single_source | |
| OEM-3-J | Rear O2 signal | lambda_nb_in | NEXUSS3-C-13 | AVI 4 | analog_in | single_source | |
| OEM-3-K | Fuel level | analog_in | NEXUSS3-C-17 | AVI 8 | analog_in | single_source | |
| OEM-3-L | Evap purge solenoid | low_side_out | NEXUSS3-A-21 | HBO 3 | hbridge_out | single_source | |
| OEM-3-M | ISC valve +14V feed | power_in | NEXUSS3-A-18 + NEXUSS3-A-25 | +12V switched input + +12V switched input | power_in | single_source | |
| OEM-3-N | Fuel pump relay | low_side_out | NEXUSS3-A-14 | DPO 3 | low_side_out | single_source | |
| OEM-3-O | ISC valve low side | low_side_out | NEXUSS3-A-16 | DPO 5 | low_side_out | single_source | |
| OEM-3-Q | VICS solenoid (intake butterflies) | low_side_out | NEXUSS3-A-22 | HBO 4 | hbridge_out | single_source | |
| OEM-3-S | EGR boost sensor | analog_in | NEXUSS3-C-18 | AVI 9 | analog_in | single_source | |
| OEM-3-T | EGR boost solenoid | low_side_out | — | — | — | single_source | |
| OEM-3-U | Canister drain cut valve (CDCV) | low_side_out | — | — | — | single_source | |
| OEM-3-V | Rear O2 heater | low_side_out | NEXUSS3-A-15 | DPO 4 | low_side_out | single_source | |
| OEM-3-W | Injector 1 | injector_out | NEXUSS3-A-1 | Injector 1 | injector_out | single_source | |
| OEM-3-X | Injector 2 | injector_out | NEXUSS3-A-2 | Injector 2 | injector_out | single_source | |
| OEM-3-Y | Injector 3 | injector_out | NEXUSS3-A-3 | Injector 3 | injector_out | single_source | |
| OEM-3-Z | Injector 4 | injector_out | NEXUSS3-A-4 | 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 | OEM-3-M | SP-14V-1 | 0.85 | no route | ISC valve +14V feed | — | |
| W3 | SP-14V-1 | NEXUSS3-A-18 | 0.85 | no route | +12V switched input | — | |
| W4 | SP-14V-1 | NEXUSS3-A-25 | 0.85 | no route | +12V switched input | — | |
| W5 | OEM-3-A | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W6 | OEM-3-B | SP-GND-1 | 0.85 | no route | Power ground | — | |
| W7 | OEM-3-C | SP-GND-1 | 0.85 | no route | Power 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-F | SP-0V-1 | 0.5 | no route | Signal ground | — | |
| W11 | SP-0V-1 | NEXUSS3-C-26 | 0.5 | no route | Signal ground | — | |
| W12 | OEM-2-I | NEXUSS3-C-25 | 0.5 | no route | +5V sensor supply | — | |
| W13 | OEM-2-J | NEXUSS3-C-1 | 0.5 | no route | Crank position (CKP) | — | |
| W14 | SP-0V-1 | NEXUSS3-C-2 | 0.5 | no route | Trigger - | — | |
| W15 | OEM-2-H | NEXUSS3-C-3 | 0.5 | no route | Cam position (CMP) | — | |
| W16 | SP-0V-1 | NEXUSS3-C-4 | 0.5 | no route | Home - | — | |
| W17 | OEM-2-F | NEXUSS3-C-23 | 0.5 | no route | Knock sensor | — | |
| W18 | OEM-3-G | NEXUSS3-A-27 | 0.5 | no route | Ignition 1 (coils 1+4, wasted spark) | — | |
| W19 | OEM-3-H | NEXUSS3-A-28 | 0.5 | no route | Ignition 2 (coils 2+3, wasted spark) | — | |
| W20 | OEM-3-W | NEXUSS3-A-1 | 0.5 | no route | Injector 1 | — | |
| W21 | OEM-3-X | NEXUSS3-A-2 | 0.5 | no route | Injector 2 | — | |
| W22 | OEM-3-Y | NEXUSS3-A-3 | 0.5 | no route | Injector 3 | — | |
| W23 | OEM-3-Z | NEXUSS3-A-4 | 0.5 | no route | Injector 4 | — | |
| W24 | OEM-1-I | NEXUSS3-A-26 | 0.5 | no route | Condenser fan relay | — | |
| W25 | OEM-1-R | NEXUSS3-A-9 | 0.5 | no route | Cooling fan relay | — | |
| W26 | OEM-1-S | NEXUSS3-A-12 | 0.5 | no route | A/C clutch relay | — | |
| W27 | OEM-3-N | NEXUSS3-A-14 | 0.5 | no route | Fuel pump relay | — | |
| W28 | OEM-1-U | NEXUSS3-C-33 | 0.5 | no route | Front O2 heater | — | |
| W29 | OEM-3-V | NEXUSS3-A-15 | 0.5 | no route | Rear O2 heater | — | |
| W30 | OEM-3-O | NEXUSS3-A-16 | 0.5 | no route | ISC valve low side | — | |
| W31 | OEM-1-E | NEXUSS3-A-17 | 0.5 | no route | Malfunction indicator lamp (MIL) | — | |
| W32 | OEM-1-O | NEXUSS3-A-5 | 0.5 | no route | Alternator control | — | |
| W33 | OEM-1-Q | NEXUSS3-A-6 | 0.5 | no route | Charge lamp | — | |
| W34 | OEM-2-M | NEXUSS3-A-7 | 0.5 | no route | EGR valve | — | |
| W35 | OEM-2-N | NEXUSS3-A-8 | 0.5 | no route | EGR valve | — | |
| W36 | OEM-2-O | NEXUSS3-A-19 | 0.5 | no route | EGR valve | — | |
| W37 | OEM-2-P | NEXUSS3-A-20 | 0.5 | no route | EGR valve | — | |
| W38 | OEM-3-L | NEXUSS3-A-21 | 0.5 | no route | Evap purge solenoid | — | |
| W39 | OEM-3-Q | NEXUSS3-A-22 | 0.5 | no route | VICS solenoid (intake butterflies) | — | |
| W40 | OEM-2-L | NEXUSS3-C-10 | 0.5 | no route | Mass air flow (MAF) | — | |
| W41 | OEM-3-E | NEXUSS3-C-11 | 0.5 | no route | Throttle position (TPS) | — | |
| W42 | OEM-2-C | NEXUSS3-C-12 | 0.5 | no route | Front O2 signal | — | |
| W43 | OEM-3-J | NEXUSS3-C-13 | 0.5 | no route | Rear O2 signal | — | |
| W44 | OEM-2-E | NEXUSS3-C-14 | 0.5 | no route | Coolant temperature (ECT) | — | |
| W45 | OEM-2-B | NEXUSS3-C-15 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W46 | OEM-2-A | NEXUSS3-C-16 | 0.5 | no route | Fuel tank pressure | — | |
| W47 | OEM-3-K | NEXUSS3-C-17 | 0.5 | no route | Fuel level | — | |
| W48 | OEM-3-S | NEXUSS3-C-18 | 0.5 | no route | EGR boost sensor | — | |
| W49 | OEM-2-D | NEXUSS3-C-5 | 0.5 | no route | Vehicle speed | — | |
| W50 | OEM-1-F | NEXUSS3-C-6 | 0.5 | no route | Brake switch | — | |
| W51 | OEM-1-G | NEXUSS3-C-7 | 0.5 | no route | Power steering pressure switch | — | |
| W52 | OEM-1-P | NEXUSS3-C-8 | 0.5 | no route | A/C request | — | |
| W53 | OEM-1-V | NEXUSS3-C-19 | 0.5 | no route | Neutral switch | — | |
| W54 | OEM-3-I | NEXUSS3-C-20 | 0.5 | no route | Clutch switch | — |
Bill of materials
| Category | Part number | Manufacturer | Description | Qty | Unit |
|---|---|---|---|---|---|
| connector | 174514-6 | TE | AMP Multilock .040/.070 hybrid 16-pin female harness plug (Miata NB1 ECU) | 1.000 | ea |
| 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 (13)
| Severity | Code | Subject | Message |
|---|---|---|---|
| warn | LOAD_UNKNOWN | NEXUSS3-A-26 | NEXUSS3-A-26 "ECR output" drives OEM-1-I Condenser fan relay (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | NET_FAMILY | OEM-2-O ↔ NEXUSS3-A-19 | OEM-2-O "EGR valve" [low_side_out] is wired to NEXUSS3-A-19 "HBO 1" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-2-P ↔ NEXUSS3-A-20 | OEM-2-P "EGR valve" [low_side_out] is wired to NEXUSS3-A-20 "HBO 2" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-3-L ↔ NEXUSS3-A-21 | OEM-3-L "Evap purge solenoid" [low_side_out] is wired to NEXUSS3-A-21 "HBO 3" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| warn | NET_FAMILY | OEM-3-Q ↔ NEXUSS3-A-22 | OEM-3-Q "VICS solenoid (intake butterflies)" [low_side_out] is wired to NEXUSS3-A-22 "HBO 4" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way. |
| info | NET_FAMILY | NEXUSS3-C-26 ↔ NEXUSS3-C-4 | NEXUSS3-C-26 "Signal ground" [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-1-O ↔ NEXUSS3-A-5 | OEM-1-O "Alternator control" [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-1-Q ↔ NEXUSS3-A-6 | OEM-1-Q "Charge lamp" [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-2-B ↔ NEXUSS3-C-15 | OEM-2-B "Intake air temperature (IAT)" [temp_in] is wired to NEXUSS3-C-15 "AVI 6" [analog_in]. Thermistor on a plain analog input needs a pull-up; check the channel can enable one. |
| info | NET_FAMILY | OEM-2-E ↔ NEXUSS3-C-14 | OEM-2-E "Coolant temperature (ECT)" [temp_in] is wired to NEXUSS3-C-14 "AVI 5" [analog_in]. Thermistor on a plain analog input needs a pull-up; check the channel can enable one. |
| info | NET_FAMILY | OEM-2-M ↔ NEXUSS3-A-7 | OEM-2-M "EGR valve" [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 | NET_FAMILY | OEM-2-N ↔ NEXUSS3-A-8 | OEM-2-N "EGR valve" [low_side_out] is wired to NEXUSS3-A-8 "Injector 8" [injector_out]. Injector drivers can usually run general low-side loads; check current and PWM frequency. |
| info | UNMAPPED | OEM | 3 optional OEM pins are not mapped: OEM-2-K Tachometer output; OEM-3-T EGR boost solenoid; OEM-3-U Canister drain cut valve (CDCV) |
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 2026-10-06. Review every wire against both manuals before building. Not wired: - OEM-1 A: Constant +12V: Haltech Nexus S3 has no battery-constant input; not needed - OEM-3 T: EGR boost solenoid: no free low_side/ls_hs/injector/hbridge on Haltech Nexus S3 - OEM-3 U: Canister drain cut valve (CDCV): no free low_side/ls_hs/injector/hbridge on Haltech Nexus S3 - OEM-2 K: 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 | 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 |
| 4 | vendor_doc | Link G4X MX5NB1X install manual (NB1 1999-00) | https://linkecu.com/documentation/MX5XNB1.pdf | archive | 2026-10-05 | 2e36c91270cc |