MX-5 Miata Mazdaspeed 2004-05 (BP-ZET turbo, no VVT) → Haltech Nexus S3 HT-213000 (auto)
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 | draft · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | 4: read the Findings page before cutting any wire |
| Size of the job | 2 wires · 3 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-AE | NEXUSS3-C-10 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-4-R | NEXUSS3-C-11 | 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 |
|---|---|---|---|---|---|
| No supply/ground nets found to cross-check. | |||||
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 | — | — | — | — | — | — | — | — |
| 10 | Battery ground | — | — | — | — | — | — | — | — |
| 11 | Battery ground | — | — | — | — | — | — | — | — |
| 12 | DPO 2 | — | — | — | — | — | — | — | — |
| 13 | Ignition switch input | — | — | — | — | — | — | — | — |
| 14 | DPO 3 | — | — | — | — | — | — | — | — |
| 15 | DPO 4 | — | — | — | — | — | — | — | — |
| 16 | DPO 5 | — | — | — | — | — | — | — | — |
| 17 | DPO 6 | — | — | — | — | — | — | — | — |
| 18 | +12V switched input | — | — | — | — | — | — | — | — |
| 19 | HBO 1 | — | — | — | — | — | — | — | — |
| 2 | Injector 2 | — | — | — | — | — | — | — | — |
| 20 | HBO 2 | — | — | — | — | — | — | — | — |
| 21 | HBO 3 | — | — | — | — | — | — | — | — |
| 22 | HBO 4 | — | — | — | — | — | — | — | — |
| 23 | CAN 1 High | — | — | — | — | — | — | — | — |
| 24 | CAN 1 Low | — | — | — | — | — | — | — | — |
| 25 | +12V switched input | — | — | — | — | — | — | — | — |
| 26 | ECR output | — | — | — | — | — | — | — | — |
| 27 | Ignition 1 | — | — | — | — | — | — | — | — |
| 28 | Ignition 2 | — | — | — | — | — | — | — | — |
| 29 | Ignition 3 | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | — | — | — | — | — | — | — |
| 30 | Ignition 4 | — | — | — | — | — | — | — | — |
| 31 | Ignition 5 | — | — | — | — | — | — | — | — |
| 32 | Ignition 6 | — | — | — | — | — | — | — | — |
| 33 | Ignition 7 | — | — | — | — | — | — | — | — |
| 34 | Ignition 8 | — | — | — | — | — | — | — | — |
| 4 | Injector 4 | — | — | — | — | — | — | — | — |
| 5 | Injector 5 | — | — | — | — | — | — | — | — |
| 6 | Injector 6 | — | — | — | — | — | — | — | — |
| 7 | Injector 7 | — | — | — | — | — | — | — | — |
| 8 | Injector 8 | — | — | — | — | — | — | — | — |
| 9 | DPO 1 | — | — | — | — | — | — | — | — |
NEXUSS3-C
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Trigger + | — | — | — | — | — | — | — | — |
| 10 | AVI 1 | — | W1 | — | 0.5 | OEM-4-AE | — | — | — |
| 11 | AVI 2 | — | W2 | — | 0.5 | OEM-4-R | — | — | — |
| 12 | AVI 3 | — | — | — | — | — | — | — | — |
| 13 | AVI 4 | — | — | — | — | — | — | — | — |
| 14 | AVI 5 | — | — | — | — | — | — | — | — |
| 15 | AVI 6 | — | — | — | — | — | — | — | — |
| 16 | AVI 7 | — | — | — | — | — | — | — | — |
| 17 | AVI 8 | — | — | — | — | — | — | — | — |
| 18 | AVI 9 | — | — | — | — | — | — | — | — |
| 19 | SPI 5 | — | — | — | — | — | — | — | — |
| 2 | Trigger - | — | — | — | — | — | — | — | — |
| 20 | SPI 6 | — | — | — | — | — | — | — | — |
| 21 | CAN 2 High | — | — | — | — | — | — | — | — |
| 22 | CAN 2 Low | — | — | — | — | — | — | — | — |
| 23 | Knock 1 | — | — | — | — | — | — | — | — |
| 24 | Knock 2 | — | — | — | — | — | — | — | — |
| 25 | +5V | — | — | — | — | — | — | — | — |
| 26 | Signal ground | — | — | — | — | — | — | — | — |
| 27 | AVI 10 | — | — | — | — | — | — | — | — |
| 28 | AVI 11 | — | — | — | — | — | — | — | — |
| 29 | WBI 1 Heater + | — | — | — | — | — | — | — | — |
| 3 | Home + | — | — | — | — | — | — | — | — |
| 30 | WBI 1 Input | — | — | — | — | — | — | — | — |
| 31 | WBI 1 Pump | — | — | — | — | — | — | — | — |
| 32 | WBI 1 Nernst | — | — | — | — | — | — | — | — |
| 33 | WBI 1 Heater - | — | — | — | — | — | — | — | — |
| 34 | WBI 1 Cal | — | — | — | — | — | — | — | — |
| 4 | Home - | — | — | — | — | — | — | — | — |
| 5 | SPI 1 | — | — | — | — | — | — | — | — |
| 6 | SPI 2 | — | — | — | — | — | — | — | — |
| 7 | SPI 3 | — | — | — | — | — | — | — | — |
| 8 | SPI 4 | — | — | — | — | — | — | — | — |
| 9 | +8V | — | — | — | — | — | — | — | — |
OEM-4
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| AC | Data link connector (DLC TEN, turbo) | — | — | — | — | — | — | — | — |
| AE | BARO/MAP sensor (turbo boost pressure) | — | W1 | — | 0.5 | NEXUSS3-C-10 | — | — | — |
| D | Boost control solenoid (turbo) | — | — | — | — | — | — | — | — |
| E | Boost control solenoid (turbo) | — | — | — | — | — | — | — | — |
| R | Intake air temperature 2 (IAT2, turbo) | — | W2 | — | 0.5 | NEXUSS3-C-11 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-4-AC | Data link connector (DLC TEN, turbo) | serial | — | — | — | BrY | single_source |
| OEM-4-AE | BARO/MAP sensor (turbo boost pressure) | analog_in | NEXUSS3-C-10 | AVI 1 | analog_in | LY | single_source |
| OEM-4-D | Boost control solenoid (turbo) | high_side_out | — | — | — | Y | single_source |
| OEM-4-E | Boost control solenoid (turbo) | high_side_out | — | — | — | Y | single_source |
| OEM-4-R | Intake air temperature 2 (IAT2, turbo) | temp_in | NEXUSS3-C-11 | AVI 2 | analog_in | VY | single_source |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-4-AE | NEXUSS3-C-10 | 0.5 | no route | BARO/MAP sensor (turbo boost pressure) | — | |
| W2 | OEM-4-R | NEXUSS3-C-11 | 0.5 | no route | Intake air temperature 2 (IAT2, turbo) | — |
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 (6)
| Severity | Code | Subject | Message |
|---|---|---|---|
| error | PHYS_REQUIRED_OPEN | NEXUSS3-A-10 | NEXUSS3-A-10 "Battery ground" is required but not wired. |
| error | PHYS_REQUIRED_OPEN | NEXUSS3-A-11 | NEXUSS3-A-11 "Battery ground" is required but not wired. |
| error | PHYS_REQUIRED_OPEN | NEXUSS3-A-18 | NEXUSS3-A-18 "+12V switched input" is required but not wired. |
| error | PHYS_REQUIRED_OPEN | NEXUSS3-A-25 | NEXUSS3-A-25 "+12V switched input" is required but not wired. |
| info | NET_FAMILY | OEM-4-R ↔ NEXUSS3-C-11 | OEM-4-R "Intake air temperature 2 (IAT2, turbo)" [temp_in] is wired to NEXUSS3-C-11 "AVI 2" [analog_in]. Thermistor on a plain analog input needs a pull-up; check the channel can enable one. |
| info | UNMAPPED | OEM | 3 optional OEM pins are not mapped: OEM-4-AC Data link connector (DLC TEN, turbo); OEM-4-D Boost control solenoid (turbo); OEM-4-E Boost control solenoid (turbo) |
Accepted (0)
| Code | Subject | Reason | By |
|---|
Notes
Auto-mapped by auto_map() from the library pin data on 2026-10-11. Review every wire against both manuals before building. Open items: - Main-relay feed: no ecu_main_power pin on the stock or the new ECU - NEXUSS3-A 10: Battery ground: required by Haltech Nexus S3 but no stock pin feeds it; wire by hand - NEXUSS3-A 11: Battery ground: required by Haltech Nexus S3 but no stock pin feeds it; wire by hand - NEXUSS3-A 18: +12V switched input: required by Haltech Nexus S3 but no stock pin feeds it; wire by hand - NEXUSS3-A 25: +12V switched input: required by Haltech Nexus S3 but no stock pin feeds it; wire by hand Not wired: - OEM-4 D: Boost control solenoid (turbo): no free high_side/ls_hs on Haltech Nexus S3 - OEM-4 E: Boost control solenoid (turbo): no free high_side/ls_hs on Haltech Nexus S3 - OEM-4 AC: Data link connector (DLC TEN, turbo): no free k_line 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 | oem_manual | 2005 Mazda MX-5 Miata Engine Performance Control System (PCM terminal voltage reference, BP and BP WITH TC) | https://trull.org/alex/pubmirror/www.mellens.net/mazda/Mazda-Miata-2005/engine_control_system.pdf | — | — | — |
| 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 | 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 |