VW Golf/Jetta Mk2 1.8 8v Digifant II → Speeduino Speeduino v0.4 (auto)
VW Golf/Jetta Mk2 1.8 8v Digifant II — Speeduino — Speeduino
⚠ NOT CHECKED. Don't build from this.
Drawn by Michael Gnankou · Rev 0 · draft · 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 | draft · not yet verified: nobody has reported building and running this harness |
|---|---|
| Open errors | 3: read the Findings page before cutting any wire |
| Size of the job | 20 wires · 4 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-13 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-A-19 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W3 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W4 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W5 | OEM-A-5 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-A-6 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | OEM-A-17 | SPEEDUINO-A-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-A-18 | SPEEDUINO-A-24 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | OEM-A-25 | SPEEDUINO-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | OEM-A-12 | SPEEDUINO-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-A-3 | SPEEDUINO-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-A-10 | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-A-22 | SPEEDUINO-A-36 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | OEM-A-23 | SPEEDUINO-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-A-2 | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-A-9 | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | OEM-A-1 | SPEEDUINO-A-18 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-A-11 | SPEEDUINO-A-14 | 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 | SPEEDUINO-A-13 | SPEEDUINO-A-12 | open (OL) | 5 V sensor reference must not touch sensor ground | |
| 2 | SPEEDUINO-A-10 | SPEEDUINO-A-13 | open (OL) | power ground 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
OEM-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Starter signal (term 50) | — | W19 | — | 0.5 | SPEEDUINO-A-18 | — | — | — |
| 10 | Coolant temperature sensor | — | W14 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| 11 | Idle/WOT throttle switch | — | W20 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| 12 | Injector driver (batch, all 4) | — | W12 | — | 0.5 | SPEEDUINO-A-1 | — | — | — |
| 13 | Ground | — | W1 | — | 0.85 | SP-GND-1 | — | — | — |
| 14 | ECU power (control-unit relay) | — | — | — | — | — | — | — | — |
| 16 | A/C compressor signal | — | — | — | — | — | — | — | — |
| 17 | AFM potentiometer supply | — | W9 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
| 18 | Hall sender signal (engine speed) | — | W10 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| 19 | Ground | — | W2 | — | 0.85 | SP-GND-1 | — | — | — |
| 2 | Oxygen (lambda) sensor signal | — | W17 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| 21 | AFM signal | — | — | — | — | — | — | — | — |
| 22 | Idle stabilizer valve coil 1 | — | W15 | — | 0.5 | SPEEDUINO-A-36 | — | — | — |
| 23 | Idle stabilizer valve coil 2 | — | W16 | — | 0.5 | SPEEDUINO-A-37 | — | — | — |
| 25 | Ignition timing signal to TCI | — | W11 | — | 0.5 | SPEEDUINO-A-7 | — | — | — |
| 3 | Fuel pump relay control | — | W13 | — | 0.5 | SPEEDUINO-A-16 | — | — | — |
| 4 | Knock sensor signal | — | — | — | — | — | — | — | — |
| 5 | Knock sensor return | — | W5 | — | 0.5 | SP-0V-1 | — | — | — |
| 6 | Sensor ground (CTS/Hall/AFM/throttle) | — | W6 | — | 0.5 | SP-0V-1 | — | — | — |
| 7 | Knock sensor shield | — | — | — | — | — | — | — | — |
| 8 | Hall sender supply (distributor) | — | — | — | — | — | — | — | — |
| 9 | Intake air temperature sensor | — | W18 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W5 | — | 0.5 | OEM-A-5 | — | — | — |
| 1 | — | — | W6 | — | 0.5 | OEM-A-6 | — | — | — |
| 1 | — | — | W7 | — | 0.5 | SPEEDUINO-A-12 | — | — | — |
| 1 | — | — | W8 | — | 0.5 | SPEEDUINO-A-23 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-A-13 | — | — | — |
| 1 | — | — | W2 | — | 0.85 | OEM-A-19 | — | — | — |
| 1 | — | — | W3 | — | 0.85 | SPEEDUINO-A-10 | — | — | — |
| 1 | — | — | W4 | — | 0.85 | SPEEDUINO-A-9 | — | — | — |
SPEEDUINO-A
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Injector 1 | — | W12 | — | 0.5 | OEM-A-12 | — | — | — |
| 10 | Ground | — | W3 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | MAP sensor (0-5V) | — | — | — | — | — | — | — | — |
| 12 | Ground | — | W7 | — | 0.5 | SP-0V-1 | — | — | — |
| 13 | 5V | — | W9 | — | 0.5 | OEM-A-17 | — | — | — |
| 14 | Proto area 1 (flex fuel) | — | W20 | — | 0.5 | OEM-A-11 | — | — | — |
| 15 | Proto area 2 (fan) | — | — | — | — | — | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | W13 | — | 0.5 | OEM-A-3 | — | — | — |
| 17 | Proto area 4 (tachometer) | — | — | — | — | — | — | — | — |
| 18 | Proto area 5 (clutch) | — | W19 | — | 0.5 | OEM-A-1 | — | — | — |
| 19 | Coolant temp (CLT) | — | W14 | — | 0.5 | OEM-A-10 | — | — | — |
| 2 | Injector 2 | — | — | — | — | — | — | — | — |
| 20 | Inlet air temp (IAT) | — | W18 | — | 0.5 | OEM-A-9 | — | — | — |
| 21 | O2 sensor | — | W17 | — | 0.5 | OEM-A-2 | — | — | — |
| 22 | TPS input | — | — | — | — | — | — | — | — |
| 23 | Ground | — | W8 | — | 0.5 | SP-0V-1 | — | — | — |
| 24 | Cam input / VR2+ | — | W10 | — | 0.5 | OEM-A-18 | — | — | — |
| 25 | Crank input / VR1+ | — | — | — | — | — | — | — | — |
| 26 | VR2- | — | — | — | — | — | — | — | — |
| 27 | VR1- | — | — | — | — | — | — | — | — |
| 28 | 5V | — | — | — | — | — | — | — | — |
| 29 | Idle stepper 2B | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | — | — | — | — | — | — | — |
| 30 | Idle stepper 2A | — | — | — | — | — | — | — | — |
| 31 | Idle stepper 1A | — | — | — | — | — | — | — | — |
| 32 | Idle stepper 1B | — | — | — | — | — | — | — | — |
| 33 | Ignition 3 | — | — | — | — | — | — | — | — |
| 34 | Ignition 2 | — | — | — | — | — | — | — | — |
| 35 | Boost | — | — | — | — | — | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | W15 | — | 0.5 | OEM-A-22 | — | — | — |
| 37 | PWM idle | — | W16 | — | 0.5 | OEM-A-23 | — | — | — |
| 38 | VVT | — | — | — | — | — | — | — | — |
| 5 | Injector 4 | — | — | — | — | — | — | — | — |
| 7 | Ignition 1 | — | W11 | — | 0.5 | OEM-A-25 | — | — | — |
| 8 | Ignition 4 | — | — | — | — | — | — | — | — |
| 9 | Ground | — | W4 | — | 0.85 | SP-GND-1 | — | — | — |
Pin map
| OEM point | OEM function | OEM family | Target point | Target function | Target family | Wire colour | Evidence |
|---|---|---|---|---|---|---|---|
| OEM-A-1 | Starter signal (term 50) | digital_in | SPEEDUINO-A-18 | Proto area 5 (clutch) | digital_in | corroborated | |
| OEM-A-10 | Coolant temperature sensor | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | corroborated | |
| OEM-A-11 | Idle/WOT throttle switch | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | corroborated | |
| OEM-A-12 | Injector driver (batch, all 4) | injector_out | SPEEDUINO-A-1 | Injector 1 | injector_out | corroborated | |
| OEM-A-13 | Ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | corroborated | |
| OEM-A-14 | ECU power (control-unit relay) | power_in | — | — | — | corroborated | |
| OEM-A-16 | A/C compressor signal | digital_in | — | — | — | corroborated | |
| OEM-A-17 | AFM potentiometer supply | vref | SPEEDUINO-A-13 | 5V | vref | corroborated | |
| OEM-A-18 | Hall sender signal (engine speed) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | corroborated | |
| OEM-A-19 | Ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | corroborated | |
| OEM-A-2 | Oxygen (lambda) sensor signal | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | corroborated | |
| OEM-A-21 | AFM signal | analog_in | — | — | — | corroborated | |
| OEM-A-22 | Idle stabilizer valve coil 1 | low_side_out | SPEEDUINO-A-36 | Idle 2 (3-wire idle) | low_side_out | corroborated | |
| OEM-A-23 | Idle stabilizer valve coil 2 | low_side_out | SPEEDUINO-A-37 | PWM idle | low_side_out | corroborated | |
| OEM-A-25 | Ignition timing signal to TCI | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | corroborated | |
| OEM-A-3 | Fuel pump relay control | low_side_out | SPEEDUINO-A-16 | Proto area 3 (fuel pump) | low_side_out | corroborated | |
| OEM-A-4 | Knock sensor signal | knock_in | — | — | — | corroborated | |
| OEM-A-5 | Knock sensor return | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-A-6 | Sensor ground (CTS/Hall/AFM/throttle) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-A-7 | Knock sensor shield | shield | — | — | — | corroborated | |
| OEM-A-8 | Hall sender supply (distributor) | power_in | — | — | — | corroborated | |
| OEM-A-9 | Intake air temperature sensor | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | corroborated |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-A-13 | SP-GND-1 | 0.85 | no route | Ground | — | |
| W2 | OEM-A-19 | SP-GND-1 | 0.85 | no route | Ground | — | |
| W3 | SP-GND-1 | SPEEDUINO-A-10 | 0.85 | no route | Ground | — | |
| W4 | SP-GND-1 | SPEEDUINO-A-9 | 0.85 | no route | Ground | — | |
| W5 | OEM-A-5 | SP-0V-1 | 0.5 | no route | Knock sensor return | — | |
| W6 | OEM-A-6 | SP-0V-1 | 0.5 | no route | Sensor ground (CTS/Hall/AFM/throttle) | — | |
| W7 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | no route | Ground | — | |
| W8 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | no route | Ground | — | |
| W9 | OEM-A-17 | SPEEDUINO-A-13 | 0.5 | no route | AFM potentiometer supply | — | |
| W10 | OEM-A-18 | SPEEDUINO-A-24 | 0.5 | no route | Hall sender signal (engine speed) | — | |
| W11 | OEM-A-25 | SPEEDUINO-A-7 | 0.5 | no route | Ignition timing signal to TCI | — | |
| W12 | OEM-A-12 | SPEEDUINO-A-1 | 0.5 | no route | Injector driver (batch, all 4) | — | |
| W13 | OEM-A-3 | SPEEDUINO-A-16 | 0.5 | no route | Fuel pump relay control | — | |
| W14 | OEM-A-10 | SPEEDUINO-A-19 | 0.5 | no route | Coolant temperature sensor | — | |
| W15 | OEM-A-22 | SPEEDUINO-A-36 | 0.5 | no route | Idle stabilizer valve coil 1 | — | |
| W16 | OEM-A-23 | SPEEDUINO-A-37 | 0.5 | no route | Idle stabilizer valve coil 2 | — | |
| W17 | OEM-A-2 | SPEEDUINO-A-21 | 0.5 | no route | Oxygen (lambda) sensor signal | — | |
| W18 | OEM-A-9 | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature sensor | — | |
| W19 | OEM-A-1 | SPEEDUINO-A-18 | 0.5 | no route | Starter signal (term 50) | — | |
| W20 | OEM-A-11 | SPEEDUINO-A-14 | 0.5 | no route | Idle/WOT throttle 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 (5)
| Severity | Code | Subject | Message |
|---|---|---|---|
| error | REQUIRED_UNMAPPED | OEM-A-14 | Required OEM function "ECU power (control-unit relay)" (power_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-A-21 | Required OEM function "AFM signal" (analog_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-A-8 | Required OEM function "Hall sender supply (distributor)" (power_in) is not connected to the new ECU. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-16 | SPEEDUINO-A-16 "Proto area 3 (fuel pump)" drives OEM-A-3 Fuel pump relay control (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| info | UNMAPPED | OEM | 3 optional OEM pins are not mapped: OEM-A-16 A/C compressor signal; OEM-A-4 Knock sensor signal; OEM-A-7 Knock sensor shield |
Accepted (0)
| Code | Subject | Reason | By |
|---|
Notes
Fit check: unconfirmed. Confirm these before building: - Trigger pattern for VW Digifant not found in the ECU's docs (No VW decoder; distributor/Hall not documented for Digifant.) - No knock input; the stock knock sensor would be unused 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 - OEM-A 21: AFM signal: no free maf/analog_0_5 on Speeduino Speeduino - OEM-A 14: ECU power (control-unit relay): no rule for class ecu_main_power; wire by hand - OEM-A 8: Hall sender supply (distributor): no rule for class sensor_supply_in; wire by hand Not wired: - OEM-A 4: Knock sensor signal: no free knock input on Speeduino Speeduino - OEM-A 7: Knock sensor shield: no shield pin on Speeduino Speeduino - OEM-A 16: A/C compressor signal: no free switch_in/frequency_in/analog_0_5 on Speeduino Speeduino
Sources
| Reliability | Kind | Title | URL | Archive | Captured | SHA-256 |
|---|---|---|---|---|---|---|
| 4 | vendor_doc | Speeduino Manual (08/04/25) — V0.4 board IDC40 pinout & features | https://speeduino.com/Speeduino_manual.pdf | archive | 2026-10-05 | 21806bd29ef0 |
| 2 | community_copy | a2resource: Digifant II engine controller pinout (VW Golf/Jetta Mk2 1.8 8v) | http://www.a2resource.com/electrical/management/digifant2.html | — | — | — |
| 2 | community_copy | drive2.ru: VW Golf Mk2 PF Digifant II ECU pinout | https://www.drive2.ru/l/9886121 | — | — | — |