VW Corrado VR6 12v (AAA) Motronic M2.9 OBD1 → Haltech Nexus S3 HT-213000 (auto)
VW Corrado VR6 12v (AAA) Motronic M2.9 OBD1 — Haltech — Nexus S3
Drawn by Michael Gnankou · Rev 0 · proposal · 2026-10-20
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 | 49 wires · 9 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-A-23 | SP-14V-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-A-38 | MAIN-R-COIL+ | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | NEW-BATT-1 | MAIN-R-IN | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | MAIN-R-COIL- | SP-GND-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | MAIN-R-OUT | NEXUSS3-A-18 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | MAIN-R-OUT | NEXUSS3-A-25 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-A-1 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | OEM-A-10 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | OEM-A-55 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-A-56 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-A-7 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | SP-GND-1 | NEXUSS3-A-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | SP-GND-1 | NEXUSS3-A-11 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-A-16 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-A-33 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-A-67 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | SP-0V-1 | NEXUSS3-C-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-A-41 | NEXUSS3-C-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-A-68 | NEXUSS3-C-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | SP-0V-1 | NEXUSS3-C-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-A-44 | NEXUSS3-C-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | SP-0V-1 | NEXUSS3-C-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-A-34 | NEXUSS3-C-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-A-8 | NEXUSS3-A-27 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-A-60 | NEXUSS3-A-28 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-A-52 | NEXUSS3-A-29 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-A-24 | NEXUSS3-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-A-3 | NEXUSS3-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-A-26 | NEXUSS3-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-A-4 | NEXUSS3-A-4 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-A-25 | NEXUSS3-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-A-2 | NEXUSS3-A-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-A-17 | NEXUSS3-C-10 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-A-40 | NEXUSS3-C-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-A-14 | NEXUSS3-C-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-A-49 | NEXUSS3-A-26 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-A-6 | NEXUSS3-A-9 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-A-9 | NEXUSS3-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-A-27 | NEXUSS3-A-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-A-31 | NEXUSS3-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W41 | OEM-A-5 | NEXUSS3-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W42 | OEM-A-53 | NEXUSS3-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W43 | OEM-A-20 | NEXUSS3-C-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W44 | OEM-A-15 | NEXUSS3-C-14 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W45 | OEM-A-36 | NEXUSS3-C-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W46 | OEM-A-65 | NEXUSS3-C-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W47 | OEM-A-37 | NEXUSS3-C-6 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W48 | OEM-A-39 | NEXUSS3-C-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W49 | NEW-KEYON-1 | NEXUSS3-A-13 | 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 | MAIN-R-COIL+ | NEXUSS3-C-25 | open (OL) | +12 V supply must not touch 5 V sensor reference | |
| 2 | MAIN-R-COIL- | MAIN-R-COIL+ | open (OL) | power ground must not touch +12 V supply | |
| 3 | MAIN-R-COIL- | MAIN-R-OUT | open (OL) | power ground must not touch +12 V supply | |
| 4 | MAIN-R-COIL- | NEW-BATT-1 | open (OL) | power ground must not touch +12 V supply | |
| 5 | MAIN-R-COIL- | NEXUSS3-C-25 | open (OL) | power ground must not touch 5 V sensor reference | |
| 6 | MAIN-R-COIL- | OEM-A-23 | open (OL) | power ground must not touch +12 V supply | |
| 7 | NEXUSS3-C-2 | MAIN-R-COIL+ | open (OL) | sensor ground must not touch +12 V supply | |
| 8 | NEXUSS3-C-2 | MAIN-R-OUT | open (OL) | sensor ground must not touch +12 V supply | |
| 9 | NEXUSS3-C-2 | NEW-BATT-1 | open (OL) | sensor ground must not touch +12 V supply | |
| 10 | NEXUSS3-C-2 | NEXUSS3-C-25 | open (OL) | sensor ground must not touch 5 V sensor reference | |
| 11 | NEXUSS3-C-2 | OEM-A-23 | open (OL) | sensor ground must not touch +12 V supply | |
| 12 | NEXUSS3-C-25 | MAIN-R-OUT | open (OL) | 5 V sensor reference must not touch +12 V supply | |
| 13 | NEXUSS3-C-25 | NEW-BATT-1 | open (OL) | 5 V sensor reference must not touch +12 V supply | |
| 14 | OEM-A-23 | NEXUSS3-C-25 | 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
MAIN-R
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| COIL+ | Relay coil positive (ignition-switched +12V) | — | W2 | — | 0.5 | OEM-A-38 | — | — | — |
| COIL- | Relay coil negative (ECU low-side driver) | — | W4 | — | 0.5 | SP-GND-1 | — | — | — |
| IN | Relay contact input (battery + via main fuse) | — | W3 | — | 0.85 | NEW-BATT-1 | — | — | — |
| OUT | Relay contact output (switched +12V bus) | — | W5 | — | 0.85 | NEXUSS3-A-18 | — | — | — |
| OUT | Relay contact output (switched +12V bus) | — | W6 | — | 0.85 | NEXUSS3-A-25 | — | — | — |
NEW-BATT
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W3 | — | 0.85 | MAIN-R-IN | — | — | — |
NEW-KEYON
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W49 | — | 0.5 | NEXUSS3-A-13 | — | — | — |
NEXUSS3-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Injector 1 | — | W27 | — | 0.5 | OEM-A-24 | — | — | — |
| 10 | Battery ground | — | W12 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | Battery ground | — | W13 | — | 0.85 | SP-GND-1 | — | — | — |
| 12 | DPO 2 | — | W38 | — | 0.5 | OEM-A-9 | — | — | — |
| 13 | Ignition switch input | — | W49 | — | 0.5 | NEW-KEYON-1 | — | — | — |
| 14 | DPO 3 | — | W39 | — | 0.5 | OEM-A-27 | — | — | — |
| 15 | DPO 4 | — | W40 | — | 0.5 | OEM-A-31 | — | — | — |
| 16 | DPO 5 | — | W41 | — | 0.5 | OEM-A-5 | — | — | — |
| 17 | DPO 6 | — | W42 | — | 0.5 | OEM-A-53 | — | — | — |
| 18 | +12V switched input | — | W5 | — | 0.85 | MAIN-R-OUT | — | — | — |
| 19 | HBO 1 | — | — | — | — | — | — | — | — |
| 2 | Injector 2 | — | W28 | — | 0.5 | OEM-A-3 | — | — | — |
| 20 | HBO 2 | — | — | — | — | — | — | — | — |
| 21 | HBO 3 | — | — | — | — | — | — | — | — |
| 22 | HBO 4 | — | — | — | — | — | — | — | — |
| 23 | CAN 1 High | — | — | — | — | — | — | — | — |
| 24 | CAN 1 Low | — | — | — | — | — | — | — | — |
| 25 | +12V switched input | — | W6 | — | 0.85 | MAIN-R-OUT | — | — | — |
| 26 | ECR output | — | W36 | — | 0.5 | OEM-A-49 | — | — | — |
| 27 | Ignition 1 | — | W24 | — | 0.5 | OEM-A-8 | — | — | — |
| 28 | Ignition 2 | — | W25 | — | 0.5 | OEM-A-60 | — | — | — |
| 29 | Ignition 3 | — | W26 | — | 0.5 | OEM-A-52 | — | — | — |
| 3 | Injector 3 | — | W29 | — | 0.5 | OEM-A-26 | — | — | — |
| 30 | Ignition 4 | — | — | — | — | — | — | — | — |
| 31 | Ignition 5 | — | — | — | — | — | — | — | — |
| 32 | Ignition 6 | — | — | — | — | — | — | — | — |
| 33 | Ignition 7 | — | — | — | — | — | — | — | — |
| 34 | Ignition 8 | — | — | — | — | — | — | — | — |
| 4 | Injector 4 | — | W30 | — | 0.5 | OEM-A-4 | — | — | — |
| 5 | Injector 5 | — | W31 | — | 0.5 | OEM-A-25 | — | — | — |
| 6 | Injector 6 | — | W32 | — | 0.5 | OEM-A-2 | — | — | — |
| 7 | Injector 7 | — | — | — | — | — | — | — | — |
| 8 | Injector 8 | — | — | — | — | — | — | — | — |
| 9 | DPO 1 | — | W37 | — | 0.5 | OEM-A-6 | — | — | — |
NEXUSS3-C
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Trigger + | — | W19 | — | 0.5 | OEM-A-68 | — | — | — |
| 10 | AVI 1 | — | W33 | — | 0.5 | OEM-A-17 | — | — | — |
| 11 | AVI 2 | — | W34 | — | 0.5 | OEM-A-40 | — | — | — |
| 12 | AVI 3 | — | W35 | — | 0.5 | OEM-A-14 | — | — | — |
| 13 | AVI 4 | — | W43 | — | 0.5 | OEM-A-20 | — | — | — |
| 14 | AVI 5 | — | W44 | — | 0.5 | OEM-A-15 | — | — | — |
| 15 | AVI 6 | — | W45 | — | 0.5 | OEM-A-36 | — | — | — |
| 16 | AVI 7 | — | — | — | — | — | — | — | — |
| 17 | AVI 8 | — | — | — | — | — | — | — | — |
| 18 | AVI 9 | — | — | — | — | — | — | — | — |
| 19 | SPI 5 | — | — | — | — | — | — | — | — |
| 2 | Trigger - | — | W20 | — | 0.5 | SP-0V-1 | — | — | — |
| 20 | SPI 6 | — | — | — | — | — | — | — | — |
| 21 | CAN 2 High | — | — | — | — | — | — | — | — |
| 22 | CAN 2 Low | — | — | — | — | — | — | — | — |
| 23 | Knock 1 | — | W23 | — | 0.5 | OEM-A-34 | — | — | — |
| 24 | Knock 2 | — | — | — | — | — | — | — | — |
| 25 | +5V | — | W18 | — | 0.5 | OEM-A-41 | — | — | — |
| 26 | Signal ground | — | W17 | — | 0.5 | SP-0V-1 | — | — | — |
| 27 | AVI 10 | — | — | — | — | — | — | — | — |
| 28 | AVI 11 | — | — | — | — | — | — | — | — |
| 29 | WBI 1 Heater + | — | — | — | — | — | — | — | — |
| 3 | Home + | — | W21 | — | 0.5 | OEM-A-44 | — | — | — |
| 30 | WBI 1 Input | — | — | — | — | — | — | — | — |
| 31 | WBI 1 Pump | — | — | — | — | — | — | — | — |
| 32 | WBI 1 Nernst | — | — | — | — | — | — | — | — |
| 33 | WBI 1 Heater - | — | — | — | — | — | — | — | — |
| 34 | WBI 1 Cal | — | — | — | — | — | — | — | — |
| 4 | Home - | — | W22 | — | 0.5 | SP-0V-1 | — | — | — |
| 5 | SPI 1 | — | W46 | — | 0.5 | OEM-A-65 | — | — | — |
| 6 | SPI 2 | — | W47 | — | 0.5 | OEM-A-37 | — | — | — |
| 7 | SPI 3 | — | W48 | — | 0.5 | OEM-A-39 | — | — | — |
| 8 | SPI 4 | — | — | — | — | — | — | — | — |
| 9 | +8V | — | — | — | — | — | — | — | — |
OEM-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Ground (E-1) | — | W7 | — | 0.85 | SP-GND-1 | — | — | — |
| 10 | Ground (OBD1 EGR enable) | — | W8 | — | 0.85 | SP-GND-1 | — | — | — |
| 14 | Coolant temperature (CLT) | — | W35 | — | 0.5 | NEXUSS3-C-12 | — | — | — |
| 15 | EGR temperature sensor | — | W44 | — | 0.5 | NEXUSS3-C-14 | — | — | — |
| 16 | MAF ground | — | W14 | — | 0.5 | SP-0V-1 | — | — | — |
| 17 | MAF signal | — | W33 | — | 0.5 | NEXUSS3-C-10 | — | — | — |
| 2 | Injector 6 (cyl 6) | — | W32 | — | 0.5 | NEXUSS3-A-6 | — | — | — |
| 20 | O2 sensor 1 (primary) | — | W43 | — | 0.5 | NEXUSS3-C-13 | — | — | — |
| 21 | Diagnostic L-line | — | — | — | — | — | — | — | — |
| 22 | Tachometer output | — | — | — | — | — | — | — | — |
| 23 | ECU main power (from engine-electronics relay) | — | W1 | — | 0.85 | SP-14V-1 | — | — | — |
| 24 | Injector 1 (cyl 1) | — | W27 | — | 0.5 | NEXUSS3-A-1 | — | — | — |
| 25 | Injector 5 (cyl 5) | — | W31 | — | 0.5 | NEXUSS3-A-5 | — | — | — |
| 26 | Injector 3 (cyl 3) | — | W29 | — | 0.5 | NEXUSS3-A-3 | — | — | — |
| 27 | Idle air control valve | — | W39 | — | 0.5 | NEXUSS3-A-14 | — | — | — |
| 3 | Injector 2 (cyl 2) | — | W28 | — | 0.5 | NEXUSS3-A-2 | — | — | — |
| 31 | EVAP canister purge valve | — | W40 | — | 0.5 | NEXUSS3-A-15 | — | — | — |
| 33 | Sensor ground bus | — | W15 | — | 0.5 | SP-0V-1 | — | — | — |
| 34 | Knock sensor 1 | — | W23 | — | 0.5 | NEXUSS3-C-23 | — | — | — |
| 36 | Intake air temperature (IAT) | — | W45 | — | 0.5 | NEXUSS3-C-15 | — | — | — |
| 37 | A/C compressor switch | — | W47 | — | 0.5 | NEXUSS3-C-6 | — | — | — |
| 38 | Ignition switch (run/start) | — | W2 | — | 0.5 | MAIN-R-COIL+ | — | — | — |
| 39 | A/C switch (cabin) | — | W48 | — | 0.5 | NEXUSS3-C-7 | — | — | — |
| 4 | Injector 4 (cyl 4) | — | W30 | — | 0.5 | NEXUSS3-A-4 | — | — | — |
| 40 | Throttle position sensor 1 | — | W34 | — | 0.5 | NEXUSS3-C-11 | — | — | — |
| 41 | TPS power (+5V) | — | W18 | — | 0.5 | NEXUSS3-C-25 | — | — | — |
| 43 | Diagnostic K-line | — | — | — | — | — | — | — | — |
| 44 | Camshaft position sensor (G40) | — | W21 | — | 0.5 | NEXUSS3-C-3 | — | — | — |
| 49 | Secondary air injection relay control | — | W36 | — | 0.5 | NEXUSS3-A-26 | — | — | — |
| 5 | Check engine light (MIL) | — | W41 | — | 0.5 | NEXUSS3-A-16 | — | — | — |
| 51 | MFA fuel-consumption signal | — | — | — | — | — | — | — | — |
| 52 | Ignition coil 4 (coil pack pin 4) | — | W26 | — | 0.5 | NEXUSS3-A-29 | — | — | — |
| 53 | Idle air control valve (2nd) | — | W42 | — | 0.5 | NEXUSS3-A-17 | — | — | — |
| 54 | Battery constant (+12V) | — | — | — | — | — | — | — | — |
| 55 | Ground (E-3) | — | W9 | — | 0.85 | SP-GND-1 | — | — | — |
| 56 | Ground (E-4) | — | W10 | — | 0.85 | SP-GND-1 | — | — | — |
| 59 | Mass airflow sensor (5th terminal) | — | — | — | — | — | — | — | — |
| 6 | Fuel pump relay control | — | W37 | — | 0.5 | NEXUSS3-A-9 | — | — | — |
| 60 | Ignition coil 3 (coil pack pin 3) | — | W25 | — | 0.5 | NEXUSS3-A-28 | — | — | — |
| 65 | Vehicle speed sensor (VSS) | — | W46 | — | 0.5 | NEXUSS3-C-5 | — | — | — |
| 67 | Crank sensor return (VR-) | — | W16 | — | 0.5 | SP-0V-1 | — | — | — |
| 68 | Crank position sensor (G28, VR+) | — | W19 | — | 0.5 | NEXUSS3-C-1 | — | — | — |
| 7 | Ground (E-2) | — | W11 | — | 0.85 | SP-GND-1 | — | — | — |
| 8 | Ignition coil 2 (coil pack pin 2) | — | W24 | — | 0.5 | NEXUSS3-A-27 | — | — | — |
| 9 | Engine electronics relay control | — | W38 | — | 0.5 | NEXUSS3-A-12 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W14 | — | 0.5 | OEM-A-16 | — | — | — |
| 1 | — | — | W15 | — | 0.5 | OEM-A-33 | — | — | — |
| 1 | — | — | W16 | — | 0.5 | OEM-A-67 | — | — | — |
| 1 | — | — | W17 | — | 0.5 | NEXUSS3-C-26 | — | — | — |
| 1 | — | — | W20 | — | 0.5 | NEXUSS3-C-2 | — | — | — |
| 1 | — | — | W22 | — | 0.5 | NEXUSS3-C-4 | — | — | — |
SP-14V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-A-23 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W4 | — | 0.5 | MAIN-R-COIL- | — | — | — |
| 1 | — | — | W7 | — | 0.85 | OEM-A-1 | — | — | — |
| 1 | — | — | W8 | — | 0.85 | OEM-A-10 | — | — | — |
| 1 | — | — | W9 | — | 0.85 | OEM-A-55 | — | — | — |
| 1 | — | — | W10 | — | 0.85 | OEM-A-56 | — | — | — |
| 1 | — | — | W11 | — | 0.85 | OEM-A-7 | — | — | — |
| 1 | — | — | W12 | — | 0.85 | NEXUSS3-A-10 | — | — | — |
| 1 | — | — | W13 | — | 0.85 | NEXUSS3-A-11 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-A-1 | Ground (E-1) | ground | MAIN-R-COIL- + NEXUSS3-A-10 + NEXUSS3-A-11 | Relay coil negative (ECU low-side driver) + Battery ground + Battery ground | ground + load | single_source | |
| OEM-A-10 | Ground (OBD1 EGR enable) | ground | MAIN-R-COIL- + NEXUSS3-A-10 + NEXUSS3-A-11 | Relay coil negative (ECU low-side driver) + Battery ground + Battery ground | ground + load | single_source | |
| OEM-A-14 | Coolant temperature (CLT) | temp_in | NEXUSS3-C-12 | AVI 3 | analog_in | single_source | |
| OEM-A-15 | EGR temperature sensor | temp_in | NEXUSS3-C-14 | AVI 5 | analog_in | single_source | |
| OEM-A-16 | MAF ground | sensor_ground | NEXUSS3-C-2 + NEXUSS3-C-26 + NEXUSS3-C-4 | Trigger - + Signal ground + Home - | sensor_ground + trigger_in | single_source | |
| OEM-A-17 | MAF signal | analog_in | NEXUSS3-C-10 | AVI 1 | analog_in | single_source | |
| OEM-A-2 | Injector 6 (cyl 6) | injector_out | NEXUSS3-A-6 | Injector 6 | injector_out | single_source | |
| OEM-A-20 | O2 sensor 1 (primary) | lambda_nb_in | NEXUSS3-C-13 | AVI 4 | analog_in | single_source | |
| OEM-A-21 | Diagnostic L-line | serial | — | — | — | single_source | |
| OEM-A-22 | Tachometer output | tacho_out | — | — | — | single_source | |
| OEM-A-23 | ECU main power (from engine-electronics relay) | power_in | — | — | — | single_source | |
| OEM-A-24 | Injector 1 (cyl 1) | injector_out | NEXUSS3-A-1 | Injector 1 | injector_out | single_source | |
| OEM-A-25 | Injector 5 (cyl 5) | injector_out | NEXUSS3-A-5 | Injector 5 | injector_out | single_source | |
| OEM-A-26 | Injector 3 (cyl 3) | injector_out | NEXUSS3-A-3 | Injector 3 | injector_out | single_source | |
| OEM-A-27 | Idle air control valve | low_side_out | NEXUSS3-A-14 | DPO 3 | low_side_out | single_source | |
| OEM-A-3 | Injector 2 (cyl 2) | injector_out | NEXUSS3-A-2 | Injector 2 | injector_out | single_source | |
| OEM-A-31 | EVAP canister purge valve | low_side_out | NEXUSS3-A-15 | DPO 4 | low_side_out | single_source | |
| OEM-A-33 | Sensor ground bus | sensor_ground | NEXUSS3-C-2 + NEXUSS3-C-26 + NEXUSS3-C-4 | Trigger - + Signal ground + Home - | sensor_ground + trigger_in | single_source | |
| OEM-A-34 | Knock sensor 1 | knock_in | NEXUSS3-C-23 | Knock 1 | knock_in | single_source | |
| OEM-A-36 | Intake air temperature (IAT) | temp_in | NEXUSS3-C-15 | AVI 6 | analog_in | single_source | |
| OEM-A-37 | A/C compressor switch | digital_in | NEXUSS3-C-6 | SPI 2 | digital_in | single_source | |
| OEM-A-38 | Ignition switch (run/start) | digital_in | MAIN-R-COIL+ | Relay coil positive (ignition-switched +12V) | power_in | single_source | |
| OEM-A-39 | A/C switch (cabin) | digital_in | NEXUSS3-C-7 | SPI 3 | digital_in | single_source | |
| OEM-A-4 | Injector 4 (cyl 4) | injector_out | NEXUSS3-A-4 | Injector 4 | injector_out | single_source | |
| OEM-A-40 | Throttle position sensor 1 | analog_in | NEXUSS3-C-11 | AVI 2 | analog_in | single_source | |
| OEM-A-41 | TPS power (+5V) | vref | NEXUSS3-C-25 | +5V | vref | single_source | |
| OEM-A-43 | Diagnostic K-line | serial | — | — | — | single_source | |
| OEM-A-44 | Camshaft position sensor (G40) | trigger_in | NEXUSS3-C-3 | Home + | trigger_in | single_source | |
| OEM-A-49 | Secondary air injection relay control | low_side_out | NEXUSS3-A-26 | ECR output | low_side_out | single_source | |
| OEM-A-5 | Check engine light (MIL) | low_side_out | NEXUSS3-A-16 | DPO 5 | low_side_out | single_source | |
| OEM-A-51 | MFA fuel-consumption signal | tacho_out | — | — | — | single_source | |
| OEM-A-52 | Ignition coil 4 (coil pack pin 4) | ignition_out | NEXUSS3-A-29 | Ignition 3 | ignition_out | single_source | |
| OEM-A-53 | Idle air control valve (2nd) | low_side_out | NEXUSS3-A-17 | DPO 6 | low_side_out | single_source | |
| OEM-A-54 | Battery constant (+12V) | power_in | — | — | — | single_source | |
| OEM-A-55 | Ground (E-3) | ground | MAIN-R-COIL- + NEXUSS3-A-10 + NEXUSS3-A-11 | Relay coil negative (ECU low-side driver) + Battery ground + Battery ground | ground + load | single_source | |
| OEM-A-56 | Ground (E-4) | ground | MAIN-R-COIL- + NEXUSS3-A-10 + NEXUSS3-A-11 | Relay coil negative (ECU low-side driver) + Battery ground + Battery ground | ground + load | single_source | |
| OEM-A-59 | Mass airflow sensor (5th terminal) | sensor_out | — | — | — | single_source | |
| OEM-A-6 | Fuel pump relay control | low_side_out | NEXUSS3-A-9 | DPO 1 | low_side_out | single_source | |
| OEM-A-60 | Ignition coil 3 (coil pack pin 3) | ignition_out | NEXUSS3-A-28 | Ignition 2 | ignition_out | single_source | |
| OEM-A-65 | Vehicle speed sensor (VSS) | digital_in | NEXUSS3-C-5 | SPI 1 | digital_in | single_source | |
| OEM-A-67 | Crank sensor return (VR-) | sensor_ground | NEXUSS3-C-2 + NEXUSS3-C-26 + NEXUSS3-C-4 | Trigger - + Signal ground + Home - | sensor_ground + trigger_in | single_source | |
| OEM-A-68 | Crank position sensor (G28, VR+) | trigger_in | NEXUSS3-C-1 | Trigger + | trigger_in | single_source | |
| OEM-A-7 | Ground (E-2) | ground | MAIN-R-COIL- + NEXUSS3-A-10 + NEXUSS3-A-11 | Relay coil negative (ECU low-side driver) + Battery ground + Battery ground | ground + load | single_source | |
| OEM-A-8 | Ignition coil 2 (coil pack pin 2) | ignition_out | NEXUSS3-A-27 | Ignition 1 | ignition_out | single_source | |
| OEM-A-9 | Engine electronics relay control | low_side_out | NEXUSS3-A-12 | DPO 2 | low_side_out | single_source |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-A-23 | SP-14V-1 | 0.85 | no route | ECU main power (from engine-electronics relay) | — | |
| W2 | OEM-A-38 | MAIN-R-COIL+ | 0.5 | no route | Ignition switch (run/start) | — | |
| W3 | NEW-BATT-1 | MAIN-R-IN | 0.85 | no route | Relay contact input (battery + via main fuse) | — | |
| W4 | MAIN-R-COIL- | SP-GND-1 | 0.5 | no route | Relay coil negative (ECU low-side driver) | — | |
| W5 | MAIN-R-OUT | NEXUSS3-A-18 | 0.85 | no route | Relay contact output (switched +12V bus) | — | |
| W6 | MAIN-R-OUT | NEXUSS3-A-25 | 0.85 | no route | Relay contact output (switched +12V bus) | — | |
| W7 | OEM-A-1 | SP-GND-1 | 0.85 | no route | Ground (E-1) | — | |
| W8 | OEM-A-10 | SP-GND-1 | 0.85 | no route | Ground (OBD1 EGR enable) | — | |
| W9 | OEM-A-55 | SP-GND-1 | 0.85 | no route | Ground (E-3) | — | |
| W10 | OEM-A-56 | SP-GND-1 | 0.85 | no route | Ground (E-4) | — | |
| W11 | OEM-A-7 | SP-GND-1 | 0.85 | no route | Ground (E-2) | — | |
| W12 | SP-GND-1 | NEXUSS3-A-10 | 0.85 | no route | Battery ground | — | |
| W13 | SP-GND-1 | NEXUSS3-A-11 | 0.85 | no route | Battery ground | — | |
| W14 | OEM-A-16 | SP-0V-1 | 0.5 | no route | MAF ground | — | |
| W15 | OEM-A-33 | SP-0V-1 | 0.5 | no route | Sensor ground bus | — | |
| W16 | OEM-A-67 | SP-0V-1 | 0.5 | no route | Crank sensor return (VR-) | — | |
| W17 | SP-0V-1 | NEXUSS3-C-26 | 0.5 | no route | Signal ground | — | |
| W18 | OEM-A-41 | NEXUSS3-C-25 | 0.5 | no route | TPS power (+5V) | — | |
| W19 | OEM-A-68 | NEXUSS3-C-1 | 0.5 | no route | Crank position sensor (G28, VR+) | — | |
| W20 | SP-0V-1 | NEXUSS3-C-2 | 0.5 | no route | Trigger - | — | |
| W21 | OEM-A-44 | NEXUSS3-C-3 | 0.5 | no route | Camshaft position sensor (G40) | — | |
| W22 | SP-0V-1 | NEXUSS3-C-4 | 0.5 | no route | Home - | — | |
| W23 | OEM-A-34 | NEXUSS3-C-23 | 0.5 | no route | Knock sensor 1 | — | |
| W24 | OEM-A-8 | NEXUSS3-A-27 | 0.5 | no route | Ignition coil 2 (coil pack pin 2) | — | |
| W25 | OEM-A-60 | NEXUSS3-A-28 | 0.5 | no route | Ignition coil 3 (coil pack pin 3) | — | |
| W26 | OEM-A-52 | NEXUSS3-A-29 | 0.5 | no route | Ignition coil 4 (coil pack pin 4) | — | |
| W27 | OEM-A-24 | NEXUSS3-A-1 | 0.5 | no route | Injector 1 (cyl 1) | — | |
| W28 | OEM-A-3 | NEXUSS3-A-2 | 0.5 | no route | Injector 2 (cyl 2) | — | |
| W29 | OEM-A-26 | NEXUSS3-A-3 | 0.5 | no route | Injector 3 (cyl 3) | — | |
| W30 | OEM-A-4 | NEXUSS3-A-4 | 0.5 | no route | Injector 4 (cyl 4) | — | |
| W31 | OEM-A-25 | NEXUSS3-A-5 | 0.5 | no route | Injector 5 (cyl 5) | — | |
| W32 | OEM-A-2 | NEXUSS3-A-6 | 0.5 | no route | Injector 6 (cyl 6) | — | |
| W33 | OEM-A-17 | NEXUSS3-C-10 | 0.5 | no route | MAF signal | — | |
| W34 | OEM-A-40 | NEXUSS3-C-11 | 0.5 | no route | Throttle position sensor 1 | — | |
| W35 | OEM-A-14 | NEXUSS3-C-12 | 0.5 | no route | Coolant temperature (CLT) | — | |
| W36 | OEM-A-49 | NEXUSS3-A-26 | 0.5 | no route | Secondary air injection relay control | — | |
| W37 | OEM-A-6 | NEXUSS3-A-9 | 0.5 | no route | Fuel pump relay control | — | |
| W38 | OEM-A-9 | NEXUSS3-A-12 | 0.5 | no route | Engine electronics relay control | — | |
| W39 | OEM-A-27 | NEXUSS3-A-14 | 0.5 | no route | Idle air control valve | — | |
| W40 | OEM-A-31 | NEXUSS3-A-15 | 0.5 | no route | EVAP canister purge valve | — | |
| W41 | OEM-A-5 | NEXUSS3-A-16 | 0.5 | no route | Check engine light (MIL) | — | |
| W42 | OEM-A-53 | NEXUSS3-A-17 | 0.5 | no route | Idle air control valve (2nd) | — | |
| W43 | OEM-A-20 | NEXUSS3-C-13 | 0.5 | no route | O2 sensor 1 (primary) | — | |
| W44 | OEM-A-15 | NEXUSS3-C-14 | 0.5 | no route | EGR temperature sensor | — | |
| W45 | OEM-A-36 | NEXUSS3-C-15 | 0.5 | no route | Intake air temperature (IAT) | — | |
| W46 | OEM-A-65 | NEXUSS3-C-5 | 0.5 | no route | Vehicle speed sensor (VSS) | — | |
| W47 | OEM-A-37 | NEXUSS3-C-6 | 0.5 | no route | A/C compressor switch | — | |
| W48 | OEM-A-39 | NEXUSS3-C-7 | 0.5 | no route | A/C switch (cabin) | — | |
| W49 | NEW-KEYON-1 | NEXUSS3-A-13 | 0.5 | no route | Ignition switch input | — |
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 (7)
| Severity | Code | Subject | Message |
|---|---|---|---|
| warn | LOAD_UNKNOWN | NEXUSS3-A-26 | NEXUSS3-A-26 "ECR output" drives OEM-A-49 Secondary air injection relay control (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| info | NET_FAMILY | OEM-A-14 ↔ NEXUSS3-C-12 | OEM-A-14 "Coolant temperature (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-A-15 ↔ NEXUSS3-C-14 | OEM-A-15 "EGR temperature sensor" [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-A-16 ↔ NEXUSS3-C-4 | OEM-A-16 "MAF 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-A-36 ↔ NEXUSS3-C-15 | OEM-A-36 "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-A-38 ↔ MAIN-R-COIL+ | OEM-A-38 "Ignition switch (run/start)" [digital_in] is wired to MAIN-R-COIL+ "Relay coil positive (ignition-switched +12V)" [power_in]. Switched supply used as the ignition-on sense. |
| info | UNMAPPED | OEM | 5 optional OEM pins are not mapped: OEM-A-21 Diagnostic L-line; OEM-A-22 Tachometer output; OEM-A-43 Diagnostic K-line; OEM-A-51 MFA fuel-consumption signal; OEM-A-59 Mass airflow sensor (5th terminal) |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-A-54 | 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 2026-10-20. Review every wire against both manuals before building. Not wired: - OEM-A 54: Battery constant (+12V): Haltech Nexus S3 has no battery-constant memory input; not needed - OEM-A 22: Tachometer output: no free tacho/frequency_out/low_side/ls_hs on Haltech Nexus S3 - OEM-A 51: MFA fuel-consumption signal: no free tacho/frequency_out/low_side/ls_hs on Haltech Nexus S3 - OEM-A 21: Diagnostic L-line: no free k_line on Haltech Nexus S3 - OEM-A 43: Diagnostic K-line: no free k_line on Haltech Nexus S3 - OEM-A 59: Mass airflow sensor (5th terminal): no rule for class sensor_signal; wire by hand
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | vendor_doc | Emtron SL4/SL6/SL8 pinout pages | https://docs.emtronaustralia.com.au/engine-management/wiring/index.html | archive | 2026-10-05 | e52b3da9996a |
| 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 | forum | rusEFI Mazda Miata 2002 engine wiring | https://github.com/rusefi/rusefi/wiki/Mazda-Miata-2002 | archive | 2026-10-05 | cc3cae670408 |
| 2 | community_copy | a2resource: VR6/ABA Motronic M2.9 (OBD1) engine control unit pinout | http://www.a2resource.com/electrical/management/motronicvr6aba.html | — | — | — |