VW Golf Mk4 1.8T 20v (AUM, Bosch ME7.5) DBW → Speeduino Speeduino v0.4 (auto)
VW Golf Mk4 1.8T 20v (AUM, Bosch ME7.5) DBW — 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 | 9: read the Findings page before cutting any wire |
| Size of the job | 44 wires · 6 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-T121-1 | SP-GND-1 | 0.85 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W2 | OEM-T121-2 | 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-T121-108 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W6 | OEM-T121-29 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W7 | OEM-T121-34 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W8 | OEM-T121-36 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W9 | OEM-T121-90 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W10 | OEM-T121-91 | SP-0V-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W11 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W12 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W13 | OEM-T121-72 | SP-5V1-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W14 | OEM-T121-83 | SP-5V1-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W15 | OEM-T121-99 | SP-5V1-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W16 | SP-5V1-1 | SPEEDUINO-A-13 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W17 | OEM-T121-73 | SP-5V2-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W18 | OEM-T121-98 | SP-5V2-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W19 | SP-5V2-1 | SPEEDUINO-A-28 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W20 | OEM-T121-82 | SPEEDUINO-A-25 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W21 | OEM-T121-86 | SPEEDUINO-A-24 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W22 | OEM-T121-102 | SPEEDUINO-A-7 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W23 | OEM-T121-95 | SPEEDUINO-A-34 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W24 | OEM-T121-103 | SPEEDUINO-A-33 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W25 | OEM-T121-94 | SPEEDUINO-A-8 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W26 | OEM-T121-96 | SPEEDUINO-A-1 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W27 | OEM-T121-89 | SPEEDUINO-A-2 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W28 | OEM-T121-97 | SPEEDUINO-A-3 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W29 | OEM-T121-88 | SPEEDUINO-A-5 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W30 | OEM-T121-118 | SPEEDUINO-A-32 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W31 | OEM-T121-117 | SPEEDUINO-A-31 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W32 | OEM-T121-101 | SPEEDUINO-A-11 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W33 | OEM-T121-33 | SPEEDUINO-A-22 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W34 | OEM-T121-93 | SPEEDUINO-A-19 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W35 | OEM-T121-65 | SPEEDUINO-A-16 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W36 | OEM-T121-66 | SPEEDUINO-A-15 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W37 | OEM-T121-5 | SPEEDUINO-A-36 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W38 | OEM-T121-63 | SPEEDUINO-A-35 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W39 | OEM-T121-104 | SPEEDUINO-A-37 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W40 | OEM-T121-105 | SPEEDUINO-A-38 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W41 | OEM-T121-37 | SPEEDUINO-A-17 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W42 | OEM-T121-68 | SPEEDUINO-A-21 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W43 | OEM-T121-85 | SPEEDUINO-A-20 | 0.5 | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | ☐ | |
| W44 | OEM-T121-54 | 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-10 | SPEEDUINO-A-13 | open (OL) | power ground must not touch 5 V sensor reference | |
| 2 | SPEEDUINO-A-10 | SPEEDUINO-A-28 | open (OL) | power ground must not touch 5 V sensor reference | |
| 3 | SPEEDUINO-A-12 | SPEEDUINO-A-13 | open (OL) | sensor ground must not touch 5 V sensor reference | |
| 4 | SPEEDUINO-A-12 | SPEEDUINO-A-28 | open (OL) | sensor 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-T121
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | ECU ground | — | W1 | — | 0.85 | SP-GND-1 | — | — | — |
| 101 | Boost pressure sensor (G31) | — | W32 | — | 0.5 | SPEEDUINO-A-11 | — | — | — |
| 102 | Ignition coil 1 (N127) | — | W22 | — | 0.5 | SPEEDUINO-A-7 | — | — | — |
| 103 | Ignition coil 3 (N158) | — | W24 | — | 0.5 | SPEEDUINO-A-33 | — | — | — |
| 104 | Boost control solenoid (N75) | — | W39 | — | 0.5 | SPEEDUINO-A-37 | — | — | — |
| 105 | Diverter valve (N249) | — | W40 | — | 0.5 | SPEEDUINO-A-38 | — | — | — |
| 106 | Knock sensor 1 (G61) | — | — | — | — | — | — | — | — |
| 107 | Knock sensor 2 (G66) | — | — | — | — | — | — | — | — |
| 108 | Sensor ground | — | W5 | — | 0.5 | SP-0V-1 | — | — | — |
| 115 | VVT camshaft adjustment valve (N205) | — | — | — | — | — | — | — | — |
| 117 | Throttle motor G186 (+) | — | W31 | — | 0.5 | SPEEDUINO-A-31 | — | — | — |
| 118 | Throttle motor G186 (−) | — | W30 | — | 0.5 | SPEEDUINO-A-32 | — | — | — |
| 121 | ECM + coil power (J271 relay feed) | — | — | — | — | — | — | — | — |
| 2 | ECU ground | — | W2 | — | 0.85 | SP-GND-1 | — | — | — |
| 21 | ECM power (J271 relay feed) | — | — | — | — | — | — | — | — |
| 27 | MAF sensor supply (G70) | — | — | — | — | — | — | — | — |
| 29 | MAF sensor ground (G70) | — | W6 | — | 0.5 | SP-0V-1 | — | — | — |
| 3 | Ignition switch +12V (term 15) | — | — | — | — | — | — | — | — |
| 33 | Accelerator pedal position 1 (G79) | — | W33 | — | 0.5 | SPEEDUINO-A-22 | — | — | — |
| 34 | Accelerator pedal position 1 ground (G79) | — | W7 | — | 0.5 | SP-0V-1 | — | — | — |
| 35 | Accelerator pedal position 2 (G185) | — | — | — | — | — | — | — | — |
| 36 | Accelerator pedal position 2 ground (G185) | — | W8 | — | 0.5 | SP-0V-1 | — | — | — |
| 37 | Engine speed signal (tacho to cluster) | — | W41 | — | 0.5 | SPEEDUINO-A-17 | — | — | — |
| 43 | K-line diagnostics (OBD pin 7) | — | — | — | — | — | — | — | — |
| 47 | Check engine light (MIL) | — | — | — | — | — | — | — | — |
| 48 | EPC warning light | — | — | — | — | — | — | — | — |
| 5 | Wideband lambda heater (Z19) | — | W37 | — | 0.5 | SPEEDUINO-A-36 | — | — | — |
| 51 | Wideband lambda pump (G39) | — | — | — | — | — | — | — | — |
| 52 | Wideband lambda pump (G39) | — | — | — | — | — | — | — | — |
| 53 | MAF sensor signal (G70) | — | — | — | — | — | — | — | — |
| 54 | Road speed signal (VSS) | — | W44 | — | 0.5 | SPEEDUINO-A-14 | — | — | — |
| 58 | CAN bus low | — | — | — | — | — | — | — | — |
| 60 | CAN bus high | — | — | — | — | — | — | — | — |
| 62 | Battery constant +12V (term 30) | — | — | — | — | — | — | — | — |
| 63 | Post-cat lambda heater (Z29) | — | W38 | — | 0.5 | SPEEDUINO-A-35 | — | — | — |
| 64 | EVAP canister valve (N80) | — | — | — | — | — | — | — | — |
| 65 | Fuel pump relay control | — | W35 | — | 0.5 | SPEEDUINO-A-16 | — | — | — |
| 66 | Secondary-air pump relay (J299) | — | W36 | — | 0.5 | SPEEDUINO-A-15 | — | — | — |
| 68 | Post-cat lambda signal (G130) | — | W42 | — | 0.5 | SPEEDUINO-A-21 | — | — | — |
| 69 | Post-cat lambda signal (G130) | — | — | — | — | — | — | — | — |
| 70 | Wideband lambda Nernst signal (G39) | — | — | — | — | — | — | — | — |
| 71 | Wideband lambda Nernst signal (G39) | — | — | — | — | — | — | — | — |
| 72 | Accelerator pedal position 1 5V supply (G79) | — | W13 | — | 0.5 | SP-5V1-1 | — | — | — |
| 73 | Accelerator pedal position 2 5V supply (G185) | — | W17 | — | 0.5 | SP-5V2-1 | — | — | — |
| 82 | Crank position sensor (G28) | — | W20 | — | 0.5 | SPEEDUINO-A-25 | — | — | — |
| 83 | Throttle position sensor 5V supply (G187/G188) | — | W14 | — | 0.5 | SP-5V1-1 | — | — | — |
| 84 | Throttle position sensor 1 (G187) | — | — | — | — | — | — | — | — |
| 85 | Intake air temperature (G42) | — | W43 | — | 0.5 | SPEEDUINO-A-20 | — | — | — |
| 86 | Camshaft position sensor (G40) | — | W21 | — | 0.5 | SPEEDUINO-A-24 | — | — | — |
| 88 | Injector 4 (N33) | — | W29 | — | 0.5 | SPEEDUINO-A-5 | — | — | — |
| 89 | Injector 2 (N31) | — | W27 | — | 0.5 | SPEEDUINO-A-2 | — | — | — |
| 9 | Secondary-air injection valve (N112) | — | — | — | — | — | — | — | — |
| 90 | Crank position sensor ground (G28) | — | W9 | — | 0.5 | SP-0V-1 | — | — | — |
| 91 | Throttle position sensor ground (G187/G188) | — | W10 | — | 0.5 | SP-0V-1 | — | — | — |
| 92 | Throttle position sensor 2 (G188) | — | — | — | — | — | — | — | — |
| 93 | Engine coolant temperature (G62) | — | W34 | — | 0.5 | SPEEDUINO-A-19 | — | — | — |
| 94 | Ignition coil 4 (N163) | — | W25 | — | 0.5 | SPEEDUINO-A-8 | — | — | — |
| 95 | Ignition coil 2 (N128) | — | W23 | — | 0.5 | SPEEDUINO-A-34 | — | — | — |
| 96 | Injector 1 (N30) | — | W26 | — | 0.5 | SPEEDUINO-A-1 | — | — | — |
| 97 | Injector 3 (N32) | — | W28 | — | 0.5 | SPEEDUINO-A-3 | — | — | — |
| 98 | Cam + boost sensor 5V supply (G40/G31) | — | W18 | — | 0.5 | SP-5V2-1 | — | — | — |
| 99 | Knock sensor 5V supply (G61/G66) | — | W15 | — | 0.5 | SP-5V1-1 | — | — | — |
SP-0V
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W5 | — | 0.5 | OEM-T121-108 | — | — | — |
| 1 | — | — | W6 | — | 0.5 | OEM-T121-29 | — | — | — |
| 1 | — | — | W7 | — | 0.5 | OEM-T121-34 | — | — | — |
| 1 | — | — | W8 | — | 0.5 | OEM-T121-36 | — | — | — |
| 1 | — | — | W9 | — | 0.5 | OEM-T121-90 | — | — | — |
| 1 | — | — | W10 | — | 0.5 | OEM-T121-91 | — | — | — |
| 1 | — | — | W11 | — | 0.5 | SPEEDUINO-A-12 | — | — | — |
| 1 | — | — | W12 | — | 0.5 | SPEEDUINO-A-23 | — | — | — |
SP-5V1
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W13 | — | 0.5 | OEM-T121-72 | — | — | — |
| 1 | — | — | W14 | — | 0.5 | OEM-T121-83 | — | — | — |
| 1 | — | — | W15 | — | 0.5 | OEM-T121-99 | — | — | — |
| 1 | — | — | W16 | — | 0.5 | SPEEDUINO-A-13 | — | — | — |
SP-5V2
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W17 | — | 0.5 | OEM-T121-73 | — | — | — |
| 1 | — | — | W18 | — | 0.5 | OEM-T121-98 | — | — | — |
| 1 | — | — | W19 | — | 0.5 | SPEEDUINO-A-28 | — | — | — |
SP-GND
| Cavity | Function | Signal | Wire | Colour | Gauge (mm²) | Destination | Terminal | Seal | Plug |
|---|---|---|---|---|---|---|---|---|---|
| 1 | — | — | W1 | — | 0.85 | OEM-T121-1 | — | — | — |
| 1 | — | — | W2 | — | 0.85 | OEM-T121-2 | — | — | — |
| 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 | — | W26 | — | 0.5 | OEM-T121-96 | — | — | — |
| 10 | Ground | — | W3 | — | 0.85 | SP-GND-1 | — | — | — |
| 11 | MAP sensor (0-5V) | — | W32 | — | 0.5 | OEM-T121-101 | — | — | — |
| 12 | Ground | — | W11 | — | 0.5 | SP-0V-1 | — | — | — |
| 13 | 5V | — | W16 | — | 0.5 | SP-5V1-1 | — | — | — |
| 14 | Proto area 1 (flex fuel) | — | W44 | — | 0.5 | OEM-T121-54 | — | — | — |
| 15 | Proto area 2 (fan) | — | W36 | — | 0.5 | OEM-T121-66 | — | — | — |
| 16 | Proto area 3 (fuel pump) | — | W35 | — | 0.5 | OEM-T121-65 | — | — | — |
| 17 | Proto area 4 (tachometer) | — | W41 | — | 0.5 | OEM-T121-37 | — | — | — |
| 18 | Proto area 5 (clutch) | — | — | — | — | — | — | — | — |
| 19 | Coolant temp (CLT) | — | W34 | — | 0.5 | OEM-T121-93 | — | — | — |
| 2 | Injector 2 | — | W27 | — | 0.5 | OEM-T121-89 | — | — | — |
| 20 | Inlet air temp (IAT) | — | W43 | — | 0.5 | OEM-T121-85 | — | — | — |
| 21 | O2 sensor | — | W42 | — | 0.5 | OEM-T121-68 | — | — | — |
| 22 | TPS input | — | W33 | — | 0.5 | OEM-T121-33 | — | — | — |
| 23 | Ground | — | W12 | — | 0.5 | SP-0V-1 | — | — | — |
| 24 | Cam input / VR2+ | — | W21 | — | 0.5 | OEM-T121-86 | — | — | — |
| 25 | Crank input / VR1+ | — | W20 | — | 0.5 | OEM-T121-82 | — | — | — |
| 26 | VR2- | — | — | — | — | — | — | — | — |
| 27 | VR1- | — | — | — | — | — | — | — | — |
| 28 | 5V | — | W19 | — | 0.5 | SP-5V2-1 | — | — | — |
| 29 | Idle stepper 2B | — | — | — | — | — | — | — | — |
| 3 | Injector 3 | — | W28 | — | 0.5 | OEM-T121-97 | — | — | — |
| 30 | Idle stepper 2A | — | — | — | — | — | — | — | — |
| 31 | Idle stepper 1A | — | W31 | — | 0.5 | OEM-T121-117 | — | — | — |
| 32 | Idle stepper 1B | — | W30 | — | 0.5 | OEM-T121-118 | — | — | — |
| 33 | Ignition 3 | — | W24 | — | 0.5 | OEM-T121-103 | — | — | — |
| 34 | Ignition 2 | — | W23 | — | 0.5 | OEM-T121-95 | — | — | — |
| 35 | Boost | — | W38 | — | 0.5 | OEM-T121-63 | — | — | — |
| 36 | Idle 2 (3-wire idle) | — | W37 | — | 0.5 | OEM-T121-5 | — | — | — |
| 37 | PWM idle | — | W39 | — | 0.5 | OEM-T121-104 | — | — | — |
| 38 | VVT | — | W40 | — | 0.5 | OEM-T121-105 | — | — | — |
| 5 | Injector 4 | — | W29 | — | 0.5 | OEM-T121-88 | — | — | — |
| 7 | Ignition 1 | — | W22 | — | 0.5 | OEM-T121-102 | — | — | — |
| 8 | Ignition 4 | — | W25 | — | 0.5 | OEM-T121-94 | — | — | — |
| 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-T121-1 | ECU ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | corroborated | |
| OEM-T121-101 | Boost pressure sensor (G31) | analog_in | SPEEDUINO-A-11 | MAP sensor (0-5V) | analog_in | corroborated | |
| OEM-T121-102 | Ignition coil 1 (N127) | ignition_out | SPEEDUINO-A-7 | Ignition 1 | ignition_out | corroborated | |
| OEM-T121-103 | Ignition coil 3 (N158) | ignition_out | SPEEDUINO-A-33 | Ignition 3 | ignition_out | corroborated | |
| OEM-T121-104 | Boost control solenoid (N75) | low_side_out | SPEEDUINO-A-37 | PWM idle | low_side_out | corroborated | |
| OEM-T121-105 | Diverter valve (N249) | low_side_out | SPEEDUINO-A-38 | VVT | low_side_out | corroborated | |
| OEM-T121-106 | Knock sensor 1 (G61) | knock_in | — | — | — | corroborated | |
| OEM-T121-107 | Knock sensor 2 (G66) | knock_in | — | — | — | corroborated | |
| OEM-T121-108 | Sensor ground | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-T121-115 | VVT camshaft adjustment valve (N205) | low_side_out | — | — | — | corroborated | |
| OEM-T121-117 | Throttle motor G186 (+) | hbridge_out | SPEEDUINO-A-31 | Idle stepper 1A | hbridge_out | corroborated | |
| OEM-T121-118 | Throttle motor G186 (−) | hbridge_out | SPEEDUINO-A-32 | Idle stepper 1B | hbridge_out | corroborated | |
| OEM-T121-121 | ECM + coil power (J271 relay feed) | power_in | — | — | — | corroborated | |
| OEM-T121-2 | ECU ground | ground | SPEEDUINO-A-10 + SPEEDUINO-A-9 | Ground + Ground | ground | corroborated | |
| OEM-T121-21 | ECM power (J271 relay feed) | power_in | — | — | — | corroborated | |
| OEM-T121-27 | MAF sensor supply (G70) | power_in | — | — | — | corroborated | |
| OEM-T121-29 | MAF sensor ground (G70) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-T121-3 | Ignition switch +12V (term 15) | digital_in | — | — | — | corroborated | |
| OEM-T121-33 | Accelerator pedal position 1 (G79) | analog_in | SPEEDUINO-A-22 | TPS input | analog_in | corroborated | |
| OEM-T121-34 | Accelerator pedal position 1 ground (G79) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-T121-35 | Accelerator pedal position 2 (G185) | analog_in | — | — | — | corroborated | |
| OEM-T121-36 | Accelerator pedal position 2 ground (G185) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-T121-37 | Engine speed signal (tacho to cluster) | tacho_out | SPEEDUINO-A-17 | Proto area 4 (tachometer) | tacho_out | corroborated | |
| OEM-T121-43 | K-line diagnostics (OBD pin 7) | serial | — | — | — | corroborated | |
| OEM-T121-47 | Check engine light (MIL) | low_side_out | — | — | — | corroborated | |
| OEM-T121-48 | EPC warning light | low_side_out | — | — | — | corroborated | |
| OEM-T121-5 | Wideband lambda heater (Z19) | low_side_out | SPEEDUINO-A-36 | Idle 2 (3-wire idle) | low_side_out | corroborated | |
| OEM-T121-51 | Wideband lambda pump (G39) | wb_ip | — | — | — | corroborated | |
| OEM-T121-52 | Wideband lambda pump (G39) | wb_ip | — | — | — | corroborated | |
| OEM-T121-53 | MAF sensor signal (G70) | analog_in | — | — | — | corroborated | |
| OEM-T121-54 | Road speed signal (VSS) | digital_in | SPEEDUINO-A-14 | Proto area 1 (flex fuel) | digital_in | corroborated | |
| OEM-T121-58 | CAN bus low | can_l | — | — | — | corroborated | |
| OEM-T121-60 | CAN bus high | can_h | — | — | — | corroborated | |
| OEM-T121-62 | Battery constant +12V (term 30) | power_in | — | — | — | corroborated | |
| OEM-T121-63 | Post-cat lambda heater (Z29) | low_side_out | SPEEDUINO-A-35 | Boost | low_side_out | corroborated | |
| OEM-T121-64 | EVAP canister valve (N80) | low_side_out | — | — | — | corroborated | |
| OEM-T121-65 | Fuel pump relay control | low_side_out | SPEEDUINO-A-16 | Proto area 3 (fuel pump) | low_side_out | corroborated | |
| OEM-T121-66 | Secondary-air pump relay (J299) | low_side_out | SPEEDUINO-A-15 | Proto area 2 (fan) | low_side_out | corroborated | |
| OEM-T121-68 | Post-cat lambda signal (G130) | lambda_nb_in | SPEEDUINO-A-21 | O2 sensor | lambda_nb_in | corroborated | |
| OEM-T121-69 | Post-cat lambda signal (G130) | lambda_nb_in | — | — | — | corroborated | |
| OEM-T121-70 | Wideband lambda Nernst signal (G39) | wb_vs | — | — | — | corroborated | |
| OEM-T121-71 | Wideband lambda Nernst signal (G39) | wb_vs | — | — | — | corroborated | |
| OEM-T121-72 | Accelerator pedal position 1 5V supply (G79) | vref | SPEEDUINO-A-13 | 5V | vref | corroborated | |
| OEM-T121-73 | Accelerator pedal position 2 5V supply (G185) | vref | SPEEDUINO-A-28 | 5V | vref | corroborated | |
| OEM-T121-82 | Crank position sensor (G28) | trigger_in | SPEEDUINO-A-25 | Crank input / VR1+ | trigger_in | corroborated | |
| OEM-T121-83 | Throttle position sensor 5V supply (G187/G188) | vref | SPEEDUINO-A-13 | 5V | vref | corroborated | |
| OEM-T121-84 | Throttle position sensor 1 (G187) | analog_in | — | — | — | corroborated | |
| OEM-T121-85 | Intake air temperature (G42) | temp_in | SPEEDUINO-A-20 | Inlet air temp (IAT) | temp_in | corroborated | |
| OEM-T121-86 | Camshaft position sensor (G40) | trigger_in | SPEEDUINO-A-24 | Cam input / VR2+ | trigger_in | corroborated | |
| OEM-T121-88 | Injector 4 (N33) | injector_out | SPEEDUINO-A-5 | Injector 4 | injector_out | corroborated | |
| OEM-T121-89 | Injector 2 (N31) | injector_out | SPEEDUINO-A-2 | Injector 2 | injector_out | corroborated | |
| OEM-T121-9 | Secondary-air injection valve (N112) | low_side_out | — | — | — | corroborated | |
| OEM-T121-90 | Crank position sensor ground (G28) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-T121-91 | Throttle position sensor ground (G187/G188) | sensor_ground | SPEEDUINO-A-12 + SPEEDUINO-A-23 | Ground + Ground | sensor_ground | corroborated | |
| OEM-T121-92 | Throttle position sensor 2 (G188) | analog_in | — | — | — | corroborated | |
| OEM-T121-93 | Engine coolant temperature (G62) | temp_in | SPEEDUINO-A-19 | Coolant temp (CLT) | temp_in | corroborated | |
| OEM-T121-94 | Ignition coil 4 (N163) | ignition_out | SPEEDUINO-A-8 | Ignition 4 | ignition_out | corroborated | |
| OEM-T121-95 | Ignition coil 2 (N128) | ignition_out | SPEEDUINO-A-34 | Ignition 2 | ignition_out | corroborated | |
| OEM-T121-96 | Injector 1 (N30) | injector_out | SPEEDUINO-A-1 | Injector 1 | injector_out | corroborated | |
| OEM-T121-97 | Injector 3 (N32) | injector_out | SPEEDUINO-A-3 | Injector 3 | injector_out | corroborated | |
| OEM-T121-98 | Cam + boost sensor 5V supply (G40/G31) | vref | SPEEDUINO-A-28 | 5V | vref | corroborated | |
| OEM-T121-99 | Knock sensor 5V supply (G61/G66) | vref | SPEEDUINO-A-13 | 5V | vref | corroborated |
Cut list
| Wire | From | To | Gauge (mm²) | Colour | Length | Signal | Ident |
|---|---|---|---|---|---|---|---|
| W1 | OEM-T121-1 | SP-GND-1 | 0.85 | no route | ECU ground | — | |
| W2 | OEM-T121-2 | SP-GND-1 | 0.85 | no route | ECU 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-T121-108 | SP-0V-1 | 0.5 | no route | Sensor ground | — | |
| W6 | OEM-T121-29 | SP-0V-1 | 0.5 | no route | MAF sensor ground (G70) | — | |
| W7 | OEM-T121-34 | SP-0V-1 | 0.5 | no route | Accelerator pedal position 1 ground (G79) | — | |
| W8 | OEM-T121-36 | SP-0V-1 | 0.5 | no route | Accelerator pedal position 2 ground (G185) | — | |
| W9 | OEM-T121-90 | SP-0V-1 | 0.5 | no route | Crank position sensor ground (G28) | — | |
| W10 | OEM-T121-91 | SP-0V-1 | 0.5 | no route | Throttle position sensor ground (G187/G188) | — | |
| W11 | SP-0V-1 | SPEEDUINO-A-12 | 0.5 | no route | Ground | — | |
| W12 | SP-0V-1 | SPEEDUINO-A-23 | 0.5 | no route | Ground | — | |
| W13 | OEM-T121-72 | SP-5V1-1 | 0.5 | no route | Accelerator pedal position 1 5V supply (G79) | — | |
| W14 | OEM-T121-83 | SP-5V1-1 | 0.5 | no route | Throttle position sensor 5V supply (G187/G188) | — | |
| W15 | OEM-T121-99 | SP-5V1-1 | 0.5 | no route | Knock sensor 5V supply (G61/G66) | — | |
| W16 | SP-5V1-1 | SPEEDUINO-A-13 | 0.5 | no route | 5V | — | |
| W17 | OEM-T121-73 | SP-5V2-1 | 0.5 | no route | Accelerator pedal position 2 5V supply (G185) | — | |
| W18 | OEM-T121-98 | SP-5V2-1 | 0.5 | no route | Cam + boost sensor 5V supply (G40/G31) | — | |
| W19 | SP-5V2-1 | SPEEDUINO-A-28 | 0.5 | no route | 5V | — | |
| W20 | OEM-T121-82 | SPEEDUINO-A-25 | 0.5 | no route | Crank position sensor (G28) | — | |
| W21 | OEM-T121-86 | SPEEDUINO-A-24 | 0.5 | no route | Camshaft position sensor (G40) | — | |
| W22 | OEM-T121-102 | SPEEDUINO-A-7 | 0.5 | no route | Ignition coil 1 (N127) | — | |
| W23 | OEM-T121-95 | SPEEDUINO-A-34 | 0.5 | no route | Ignition coil 2 (N128) | — | |
| W24 | OEM-T121-103 | SPEEDUINO-A-33 | 0.5 | no route | Ignition coil 3 (N158) | — | |
| W25 | OEM-T121-94 | SPEEDUINO-A-8 | 0.5 | no route | Ignition coil 4 (N163) | — | |
| W26 | OEM-T121-96 | SPEEDUINO-A-1 | 0.5 | no route | Injector 1 (N30) | — | |
| W27 | OEM-T121-89 | SPEEDUINO-A-2 | 0.5 | no route | Injector 2 (N31) | — | |
| W28 | OEM-T121-97 | SPEEDUINO-A-3 | 0.5 | no route | Injector 3 (N32) | — | |
| W29 | OEM-T121-88 | SPEEDUINO-A-5 | 0.5 | no route | Injector 4 (N33) | — | |
| W30 | OEM-T121-118 | SPEEDUINO-A-32 | 0.5 | no route | Throttle motor G186 (−) | — | |
| W31 | OEM-T121-117 | SPEEDUINO-A-31 | 0.5 | no route | Throttle motor G186 (+) | — | |
| W32 | OEM-T121-101 | SPEEDUINO-A-11 | 0.5 | no route | Boost pressure sensor (G31) | — | |
| W33 | OEM-T121-33 | SPEEDUINO-A-22 | 0.5 | no route | Accelerator pedal position 1 (G79) | — | |
| W34 | OEM-T121-93 | SPEEDUINO-A-19 | 0.5 | no route | Engine coolant temperature (G62) | — | |
| W35 | OEM-T121-65 | SPEEDUINO-A-16 | 0.5 | no route | Fuel pump relay control | — | |
| W36 | OEM-T121-66 | SPEEDUINO-A-15 | 0.5 | no route | Secondary-air pump relay (J299) | — | |
| W37 | OEM-T121-5 | SPEEDUINO-A-36 | 0.5 | no route | Wideband lambda heater (Z19) | — | |
| W38 | OEM-T121-63 | SPEEDUINO-A-35 | 0.5 | no route | Post-cat lambda heater (Z29) | — | |
| W39 | OEM-T121-104 | SPEEDUINO-A-37 | 0.5 | no route | Boost control solenoid (N75) | — | |
| W40 | OEM-T121-105 | SPEEDUINO-A-38 | 0.5 | no route | Diverter valve (N249) | — | |
| W41 | OEM-T121-37 | SPEEDUINO-A-17 | 0.5 | no route | Engine speed signal (tacho to cluster) | — | |
| W42 | OEM-T121-68 | SPEEDUINO-A-21 | 0.5 | no route | Post-cat lambda signal (G130) | — | |
| W43 | OEM-T121-85 | SPEEDUINO-A-20 | 0.5 | no route | Intake air temperature (G42) | — | |
| W44 | OEM-T121-54 | SPEEDUINO-A-14 | 0.5 | no route | Road speed signal (VSS) | — |
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 (18)
| Severity | Code | Subject | Message |
|---|---|---|---|
| error | REQUIRED_UNMAPPED | OEM-T121-106 | Required OEM function "Knock sensor 1 (G61)" (knock_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-107 | Required OEM function "Knock sensor 2 (G66)" (knock_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-121 | Required OEM function "ECM + coil power (J271 relay feed)" (power_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-21 | Required OEM function "ECM power (J271 relay feed)" (power_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-3 | Required OEM function "Ignition switch +12V (term 15)" (digital_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-35 | Required OEM function "Accelerator pedal position 2 (G185)" (analog_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-53 | Required OEM function "MAF sensor signal (G70)" (analog_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-84 | Required OEM function "Throttle position sensor 1 (G187)" (analog_in) is not connected to the new ECU. |
| error | REQUIRED_UNMAPPED | OEM-T121-92 | Required OEM function "Throttle position sensor 2 (G188)" (analog_in) is not connected to the new ECU. |
| warn | DBW_MOTOR_CURRENT | SPEEDUINO-A-31 | Cannot confirm Speeduino can drive the throttle motor: neither the motor stall current (OEM-T121-117) nor the peak rating of SPEEDUINO-A-31 "Idle stepper 1A" is known. |
| warn | DBW_MOTOR_CURRENT | SPEEDUINO-A-32 | Cannot confirm Speeduino can drive the throttle motor: neither the motor stall current (OEM-T121-118) nor the peak rating of SPEEDUINO-A-32 "Idle stepper 1B" is known. |
| warn | DBW_SHARED_5V | OEM-T121-72 + OEM-T121-83 + OEM-T121-99 + SP-5V1-1 + SPEEDUINO-A-13 | These 5 V supplies are separate in the stock car (OEM-T121-72 [pedal1], OEM-T121-83 [tps], OEM-T121-99 [knock]) and here share one ECU 5 V (SPEEDUINO-A-13). On a drive-by-wire car the OEM splits them so one short or fault can't corrupt both throttle/pedal tracks at once. Speeduino has 2 5 V sensor supply pin(s). All are in use, so decide: accept the shared supply (and rely on the ECU's DBW fault checks), or add a separate regulated 5 V for the sub tracks. |
| warn | DBW_SHARED_5V | OEM-T121-73 + OEM-T121-98 + SP-5V2-1 + SPEEDUINO-A-28 | These 5 V supplies are separate in the stock car (OEM-T121-73 [pedal2], OEM-T121-98 [cam_boost]) and here share one ECU 5 V (SPEEDUINO-A-28). On a drive-by-wire car the OEM splits them so one short or fault can't corrupt both throttle/pedal tracks at once. Speeduino has 2 5 V sensor supply pin(s). All are in use, so decide: accept the shared supply (and rely on the ECU's DBW fault checks), or add a separate regulated 5 V for the sub tracks. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-15 | SPEEDUINO-A-15 "Proto area 2 (fan)" drives OEM-T121-66 Secondary-air pump relay (J299) (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | LOAD_UNKNOWN | SPEEDUINO-A-16 | SPEEDUINO-A-16 "Proto area 3 (fuel pump)" drives OEM-T121-65 Fuel pump relay control (load 0.2 A) but its current rating is unknown. Check the ECU manual. |
| warn | SUPPLY_GROUP | OEM-T121-72 + OEM-T121-83 + OEM-T121-99 + SP-5V1-1 + SPEEDUINO-A-13 | Supplies meant to stay independent share one net: OEM-T121-72 [pedal1], OEM-T121-83 [tps], OEM-T121-99 [knock]. The new ECU has no free 5 V reference, so they share one: normal on a standalone, but a short on any of these sensors drops them all. |
| warn | SUPPLY_GROUP | OEM-T121-73 + OEM-T121-98 + SP-5V2-1 + SPEEDUINO-A-28 | Supplies meant to stay independent share one net: OEM-T121-73 [pedal2], OEM-T121-98 [cam_boost]. The new ECU has no free 5 V reference, so they share one: normal on a standalone, but a short on any of these sensors drops them all. |
| info | UNMAPPED | OEM | 14 optional OEM pins are not mapped: OEM-T121-115 VVT camshaft adjustment valve (N205); OEM-T121-27 MAF sensor supply (G70); OEM-T121-43 K-line diagnostics (OBD pin 7); OEM-T121-47 Check engine light (MIL); OEM-T121-48 EPC warning light; OEM-T121-51 Wideband lambda pump (G39); OEM-T121-52 Wideband lambda pump (G39); OEM-T121-58 CAN bus low; OEM-T121-60 CAN bus high; OEM-T121-64 EVAP canister valve (N80); OEM-T121-69 Post-cat lambda signal (G130); OEM-T121-70 Wideband lambda Nernst signal (G39); OEM-T121-71 Wideband lambda Nernst signal (G39); OEM-T121-9 Secondary-air injection valve (N112) |
Accepted (1)
| Code | Subject | Reason | By |
|---|---|---|---|
| REQUIRED_UNMAPPED | OEM-T121-62 | Battery-constant (memory) feed of the stock ECU: the new ECU has no such input, so it is not needed. | mapping-proposal |
Notes
Fit check: needs add-on. Resolve these before building: - No drive-by-wire; needs a cable-throttle conversion or an external DBW controller - Trigger pattern for VW EA113 not found in the ECU's docs (No VW decoder (1.8T 20v).) - No knock input; the stock knock sensor would be unused - This car has VW/Audi Immobilizer (delete/bypass for standalone) immobilizer; needs a delete/bypass 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-T121 106: Knock sensor 1 (G61): no free knock input on Speeduino Speeduino - OEM-T121 107: Knock sensor 2 (G66): no free knock input on Speeduino Speeduino - OEM-T121 3: Ignition switch +12V (term 15): key-on 12 V sense — optional in a swap (the main relay is energized from keyed 12 V, not from this pin); Speeduino Speeduino has no dedicated key-on input - OEM-T121 53: MAF sensor signal (G70): no free maf/analog_0_5 on Speeduino Speeduino - OEM-T121 84: Throttle position sensor 1 (G187): no free tps/analog_0_5 on Speeduino Speeduino - OEM-T121 35: Accelerator pedal position 2 (G185): no free tps/analog_0_5 on Speeduino Speeduino - OEM-T121 92: Throttle position sensor 2 (G188): no free tps/analog_0_5 on Speeduino Speeduino - OEM-T121 121: ECM + coil power (J271 relay feed): no rule for class ecu_main_power; wire by hand - OEM-T121 21: ECM power (J271 relay feed): no rule for class ecu_main_power; wire by hand Not wired: - OEM-T121 62: Battery constant +12V (term 30): Speeduino Speeduino has no battery-constant input; not needed - OEM-T121 115: VVT camshaft adjustment valve (N205): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-T121 47: Check engine light (MIL): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-T121 48: EPC warning light: no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-T121 64: EVAP canister valve (N80): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-T121 9: Secondary-air injection valve (N112): no free low_side/relay_control/heater_low_side/ls_hs/injector on Speeduino Speeduino - OEM-T121 51: Wideband lambda pump (G39): no free wb_ip on Speeduino Speeduino - OEM-T121 52: Wideband lambda pump (G39): no free wb_ip on Speeduino Speeduino - OEM-T121 70: Wideband lambda Nernst signal (G39): no free wb_vs on Speeduino Speeduino - OEM-T121 71: Wideband lambda Nernst signal (G39): no free wb_vs on Speeduino Speeduino - OEM-T121 69: Post-cat lambda signal (G130): no free o2_narrowband/analog_0_5 on Speeduino Speeduino - OEM-T121 60: CAN bus high: no free can_h on Speeduino Speeduino - OEM-T121 58: CAN bus low: no free can_l on Speeduino Speeduino - OEM-T121 43: K-line diagnostics (OBD pin 7): no free k_line on Speeduino Speeduino - OEM-T121 27: MAF sensor supply (G70): no rule for class sensor_supply_in; wire by hand
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 |
| 3 | community_copy | NefMoto: ME7.5 ECU bench-flashing power/ground pins | http://nefmoto.com/wiki/index.php?title=ECU_Bench_Flashing | — | — | — |
| 3 | community_copy | vwressources: Bosch Motronic ME7.5 (AMK/ARY/AUQ/ARX/AUM) T121 pinout | https://www.vwressources.planethoster.world/me75_pinout.html | — | — | — |