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VW Golf Mk4 1.8T 20v (AUM, Bosch ME7.5) DBW → DTAFast T4 (auto)

VW Golf Mk4 1.8T 20v (AUM, Bosch ME7.5) DBW — DTAFast — T4
⚠ NOT CHECKED. Don't build from this.
Drawn by Michael Gnankou · Rev 0 · draft · 2026-10-11

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.

Statusdraft · not yet verified: nobody has reported building and running this harness
Open errors6: read the Findings page before cutting any wire
Size of the job57 wires · 9 connectors · 2 part lines
ToolsCrimp and extraction tools for each terminal family (see Connectors) · wire strippers · multimeter · heat gun + heat-shrink
Terminals3-1447221-4
Order of work1. 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.

WireFromToGaugeColourCutLabelCrimp ACrimp BPin APin BContinuity
W1OEM-T121-121SP-14V-10.85☐☐☐☐☐☐☐
W2OEM-T121-21SP-14V-10.85☐☐☐☐☐☐☐
W3SP-14V-1T4-C1-310.85☐☐☐☐☐☐☐
W4OEM-T121-62T4-C3-260.85☐☐☐☐☐☐☐
W5OEM-T121-1SP-GND-10.85☐☐☐☐☐☐☐
W6OEM-T121-2SP-GND-10.85☐☐☐☐☐☐☐
W7SP-GND-1T4-C1-130.85☐☐☐☐☐☐☐
W8SP-GND-1T4-C1-140.85☐☐☐☐☐☐☐
W9OEM-T121-108SP-0V-10.5☐☐☐☐☐☐☐
W10OEM-T121-29SP-0V-10.5☐☐☐☐☐☐☐
W11OEM-T121-34SP-0V-10.5☐☐☐☐☐☐☐
W12OEM-T121-36SP-0V-10.5☐☐☐☐☐☐☐
W13OEM-T121-90SP-0V-10.5☐☐☐☐☐☐☐
W14OEM-T121-91SP-0V-10.5☐☐☐☐☐☐☐
W15SP-0V-1T4-C2-210.5☐☐☐☐☐☐☐
W16SP-0V-1T4-C2-330.5☐☐☐☐☐☐☐
W17OEM-T121-72SP-5V1-10.5☐☐☐☐☐☐☐
W18OEM-T121-98SP-5V1-10.5☐☐☐☐☐☐☐
W19SP-5V1-1T4-C2-240.5☐☐☐☐☐☐☐
W20OEM-T121-73SP-5V2-10.5☐☐☐☐☐☐☐
W21OEM-T121-83SP-5V2-10.5☐☐☐☐☐☐☐
W22OEM-T121-99SP-5V2-10.5☐☐☐☐☐☐☐
W23SP-5V2-1T4-C2-90.5☐☐☐☐☐☐☐
W24OEM-T121-82T4-C2-120.5☐☐☐☐☐☐☐
W25OEM-T121-86T4-C2-220.5☐☐☐☐☐☐☐
W26OEM-T121-102T4-C1-100.5☐☐☐☐☐☐☐
W27OEM-T121-95T4-C1-180.5☐☐☐☐☐☐☐
W28OEM-T121-103T4-C1-10.5☐☐☐☐☐☐☐
W29OEM-T121-94T4-C1-260.5☐☐☐☐☐☐☐
W30OEM-T121-96T4-C1-90.5☐☐☐☐☐☐☐
W31OEM-T121-89T4-C1-170.5☐☐☐☐☐☐☐
W32OEM-T121-97T4-C1-340.5☐☐☐☐☐☐☐
W33OEM-T121-88T4-C1-250.5☐☐☐☐☐☐☐
W34OEM-T121-53T4-C2-100.5☐☐☐☐☐☐☐
W35OEM-T121-101T4-C2-10.5☐☐☐☐☐☐☐
W36OEM-T121-33T4-C2-50.5☐☐☐☐☐☐☐
W37OEM-T121-84T4-C2-60.5☐☐☐☐☐☐☐
W38OEM-T121-35T4-C2-190.5☐☐☐☐☐☐☐
W39OEM-T121-92T4-C3-170.5☐☐☐☐☐☐☐
W40OEM-T121-93T4-C2-70.5☐☐☐☐☐☐☐
W41OEM-T121-65T4-C1-50.5☐☐☐☐☐☐☐
W42OEM-T121-66T4-C1-40.5☐☐☐☐☐☐☐
W43OEM-T121-5T4-C3-90.5☐☐☐☐☐☐☐
W44OEM-T121-63T4-C1-30.5☐☐☐☐☐☐☐
W45OEM-T121-104T4-C3-220.5☐☐☐☐☐☐☐
W46OEM-T121-105T4-C3-230.5☐☐☐☐☐☐☐
W47OEM-T121-115T4-C3-240.5☐☐☐☐☐☐☐
W48OEM-T121-47T4-C3-250.5☐☐☐☐☐☐☐
W49OEM-T121-48T4-C3-100.5☐☐☐☐☐☐☐
W50OEM-T121-51T4-C3-70.5☐☐☐☐☐☐☐
W51OEM-T121-70T4-C3-120.5☐☐☐☐☐☐☐
W52OEM-T121-68T4-C3-180.5☐☐☐☐☐☐☐
W53OEM-T121-69T4-C2-340.5☐☐☐☐☐☐☐
W54OEM-T121-85T4-C2-250.5☐☐☐☐☐☐☐
W55OEM-T121-54T4-C2-20.5☐☐☐☐☐☐☐
W56OEM-T121-60T4-C2-260.5☐☐☐☐☐☐☐
W57OEM-T121-58T4-C2-280.5☐☐☐☐☐☐☐

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 AProbe BExpectWhyReading
1T4-C1-13T4-C1-31open (OL)power ground must not touch +12 V supply
2T4-C1-13T4-C2-24open (OL)power ground must not touch 5 V sensor reference
3T4-C1-13T4-C2-9open (OL)power ground must not touch 5 V sensor reference
4T4-C1-13T4-C3-26open (OL)power ground must not touch +12 V supply
5T4-C1-31T4-C2-24open (OL)+12 V supply must not touch 5 V sensor reference
6T4-C1-31T4-C2-9open (OL)+12 V supply must not touch 5 V sensor reference
7T4-C2-21T4-C1-31open (OL)sensor ground must not touch +12 V supply
8T4-C2-21T4-C2-24open (OL)sensor ground must not touch 5 V sensor reference
9T4-C2-21T4-C2-9open (OL)sensor ground must not touch 5 V sensor reference
10T4-C2-21T4-C3-26open (OL)sensor ground must not touch +12 V supply
11T4-C3-26T4-C2-24open (OL)+12 V supply must not touch 5 V sensor reference
12T4-C3-26T4-C2-9open (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

RevLabelByDate
No revisions yet.

Schematic

OEM-T121SP-0VSP-14VSP-5V1SP-5V2SP-GNDT4-C1T4-C2T4-C3

Connectors

OEM-T121

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1ECU ground—W5—0.85SP-GND-1———
101Boost pressure sensor (G31)—W35—0.5T4-C2-1———
102Ignition coil 1 (N127)—W26—0.5T4-C1-10———
103Ignition coil 3 (N158)—W28—0.5T4-C1-1———
104Boost control solenoid (N75)—W45—0.5T4-C3-22———
105Diverter valve (N249)—W46—0.5T4-C3-23———
106Knock sensor 1 (G61)————————
107Knock sensor 2 (G66)————————
108Sensor ground—W9—0.5SP-0V-1———
115VVT camshaft adjustment valve (N205)—W47—0.5T4-C3-24———
117Throttle motor G186 (+)————————
118Throttle motor G186 (−)————————
121ECM + coil power (J271 relay feed)—W1—0.85SP-14V-1———
2ECU ground—W6—0.85SP-GND-1———
21ECM power (J271 relay feed)—W2—0.85SP-14V-1———
27MAF sensor supply (G70)————————
29MAF sensor ground (G70)—W10—0.5SP-0V-1———
3Ignition switch +12V (term 15)————————
33Accelerator pedal position 1 (G79)—W36—0.5T4-C2-5———
34Accelerator pedal position 1 ground (G79)—W11—0.5SP-0V-1———
35Accelerator pedal position 2 (G185)—W38—0.5T4-C2-19———
36Accelerator pedal position 2 ground (G185)—W12—0.5SP-0V-1———
37Engine speed signal (tacho to cluster)————————
43K-line diagnostics (OBD pin 7)————————
47Check engine light (MIL)—W48—0.5T4-C3-25———
48EPC warning light—W49—0.5T4-C3-10———
5Wideband lambda heater (Z19)—W43—0.5T4-C3-9———
51Wideband lambda pump (G39)—W50—0.5T4-C3-7———
52Wideband lambda pump (G39)————————
53MAF sensor signal (G70)—W34—0.5T4-C2-10———
54Road speed signal (VSS)—W55—0.5T4-C2-2———
58CAN bus low—W57—0.5T4-C2-28———
60CAN bus high—W56—0.5T4-C2-26———
62Battery constant +12V (term 30)—W4—0.85T4-C3-26———
63Post-cat lambda heater (Z29)—W44—0.5T4-C1-3———
64EVAP canister valve (N80)————————
65Fuel pump relay control—W41—0.5T4-C1-5———
66Secondary-air pump relay (J299)—W42—0.5T4-C1-4———
68Post-cat lambda signal (G130)—W52—0.5T4-C3-18———
69Post-cat lambda signal (G130)—W53—0.5T4-C2-34———
70Wideband lambda Nernst signal (G39)—W51—0.5T4-C3-12———
71Wideband lambda Nernst signal (G39)————————
72Accelerator pedal position 1 5V supply (G79)—W17—0.5SP-5V1-1———
73Accelerator pedal position 2 5V supply (G185)—W20—0.5SP-5V2-1———
82Crank position sensor (G28)—W24—0.5T4-C2-12———
83Throttle position sensor 5V supply (G187/G188)—W21—0.5SP-5V2-1———
84Throttle position sensor 1 (G187)—W37—0.5T4-C2-6———
85Intake air temperature (G42)—W54—0.5T4-C2-25———
86Camshaft position sensor (G40)—W25—0.5T4-C2-22———
88Injector 4 (N33)—W33—0.5T4-C1-25———
89Injector 2 (N31)—W31—0.5T4-C1-17———
9Secondary-air injection valve (N112)————————
90Crank position sensor ground (G28)—W13—0.5SP-0V-1———
91Throttle position sensor ground (G187/G188)—W14—0.5SP-0V-1———
92Throttle position sensor 2 (G188)—W39—0.5T4-C3-17———
93Engine coolant temperature (G62)—W40—0.5T4-C2-7———
94Ignition coil 4 (N163)—W29—0.5T4-C1-26———
95Ignition coil 2 (N128)—W27—0.5T4-C1-18———
96Injector 1 (N30)—W30—0.5T4-C1-9———
97Injector 3 (N32)—W32—0.5T4-C1-34———
98Cam + boost sensor 5V supply (G40/G31)—W18—0.5SP-5V1-1———
99Knock sensor 5V supply (G61/G66)—W22—0.5SP-5V2-1———

SP-0V

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W10—0.5OEM-T121-29———
1——W9—0.5OEM-T121-108———
1——W11—0.5OEM-T121-34———
1——W12—0.5OEM-T121-36———
1——W13—0.5OEM-T121-90———
1——W14—0.5OEM-T121-91———
1——W15—0.5T4-C2-21———
1——W16—0.5T4-C2-33———

SP-14V

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W1—0.85OEM-T121-121———
1——W2—0.85OEM-T121-21———
1——W3—0.85T4-C1-31———

SP-5V1

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W17—0.5OEM-T121-72———
1——W18—0.5OEM-T121-98———
1——W19—0.5T4-C2-24———

SP-5V2

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W20—0.5OEM-T121-73———
1——W21—0.5OEM-T121-83———
1——W22—0.5OEM-T121-99———
1——W23—0.5T4-C2-9———

SP-GND

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W5—0.85OEM-T121-1———
1——W6—0.85OEM-T121-2———
1——W7—0.85T4-C1-13———
1——W8—0.85T4-C1-14———

T4-C1

Mating face
T4-C1-1 · Coil 31T4-C1-22T4-C1-3 · PWM 33T4-C1-4 · PWM 24T4-C1-5 · PWM 15T4-C1-66T4-C1-77T4-C1-88T4-C1-9 · Injector 19T4-C1-10 · Coil 110T4-C1-1111T4-C1-1212T4-C1-13 · Power Ground 113T4-C1-14 · Power Ground 214T4-C1-1515T4-C1-1616T4-C1-17 · Injector 217T4-C1-18 · Coil 218T4-C1-1919T4-C1-2020T4-C1-2121T4-C1-2222T4-C1-2323T4-C1-2424T4-C1-25 · Injector 425T4-C1-26 · Coil 426T4-C1-2727T4-C1-2828T4-C1-2929T4-C1-3030T4-C1-31 · Ignition 12v In31T4-C1-3232T4-C1-3333T4-C1-34 · Injector 334
Wire side
T4-C1-1 · Coil 31T4-C1-22T4-C1-3 · PWM 33T4-C1-4 · PWM 24T4-C1-5 · PWM 15T4-C1-66T4-C1-77T4-C1-88T4-C1-9 · Injector 19T4-C1-10 · Coil 110T4-C1-1111T4-C1-1212T4-C1-13 · Power Ground 113T4-C1-14 · Power Ground 214T4-C1-1515T4-C1-1616T4-C1-17 · Injector 217T4-C1-18 · Coil 218T4-C1-1919T4-C1-2020T4-C1-2121T4-C1-2222T4-C1-2323T4-C1-2424T4-C1-25 · Injector 425T4-C1-26 · Coil 426T4-C1-2727T4-C1-2828T4-C1-2929T4-C1-3030T4-C1-31 · Ignition 12v In31T4-C1-3232T4-C1-3333T4-C1-34 · Injector 334
CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1Coil 3—W28—0.5OEM-T121-103———
2—————————
3PWM 3—W44—0.5OEM-T121-63———
4PWM 2—W42—0.5OEM-T121-66———
5PWM 1—W41—0.5OEM-T121-65———
6—————————
7—————————
8—————————
9Injector 1—W30—0.5OEM-T121-96———
10Coil 1—W26—0.5OEM-T121-102———
11—————————
12—————————
13Power Ground 1—W7—0.85SP-GND-1———
14Power Ground 2—W8—0.85SP-GND-1———
15—————————
16—————————
17Injector 2—W31—0.5OEM-T121-89———
18Coil 2—W27—0.5OEM-T121-95———
19—————————
20—————————
21—————————
22—————————
23—————————
24—————————
25Injector 4—W33—0.5OEM-T121-88———
26Coil 4—W29—0.5OEM-T121-94———
27—————————
28—————————
29—————————
30—————————
31Ignition 12v In—W3—0.85SP-14V-1———
32—————————
33—————————
34Injector 3—W32—0.5OEM-T121-97———

T4-C2

Mating face
T4-C2-1 · Analogue 21T4-C2-2 · Wheel 12T4-C2-3 · Analogue 103T4-C2-4 · Digital 14T4-C2-5 · Analogue 35T4-C2-6 · Analogue 46T4-C2-7 · Thermistor 17T4-C2-88T4-C2-9 · 5v Output9T4-C2-10 · Analogue 110T4-C2-1111T4-C2-12 · Crank12T4-C2-1313T4-C2-14 · Digital 414T4-C2-15 · Digital 515T4-C2-16 · Analogue 1116T4-C2-17 · Thermistor 317T4-C2-1818T4-C2-19 · Analogue 619T4-C2-2020T4-C2-21 · Sensor Ground21T4-C2-22 · Cam 122T4-C2-2323T4-C2-24 · 5v Output24T4-C2-25 · Thermistor 225T4-C2-26 · CAN High26T4-C2-2727T4-C2-28 · CAN Low28T4-C2-2929T4-C2-3030T4-C2-3131T4-C2-3232T4-C2-33 · Sensor Ground33T4-C2-34 · Analogue 934
Wire side
T4-C2-1 · Analogue 21T4-C2-2 · Wheel 12T4-C2-3 · Analogue 103T4-C2-4 · Digital 14T4-C2-5 · Analogue 35T4-C2-6 · Analogue 46T4-C2-7 · Thermistor 17T4-C2-88T4-C2-9 · 5v Output9T4-C2-10 · Analogue 110T4-C2-1111T4-C2-12 · Crank12T4-C2-1313T4-C2-14 · Digital 414T4-C2-15 · Digital 515T4-C2-16 · Analogue 1116T4-C2-17 · Thermistor 317T4-C2-1818T4-C2-19 · Analogue 619T4-C2-2020T4-C2-21 · Sensor Ground21T4-C2-22 · Cam 122T4-C2-2323T4-C2-24 · 5v Output24T4-C2-25 · Thermistor 225T4-C2-26 · CAN High26T4-C2-2727T4-C2-28 · CAN Low28T4-C2-2929T4-C2-3030T4-C2-3131T4-C2-3232T4-C2-33 · Sensor Ground33T4-C2-34 · Analogue 934
CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1Analogue 2—W35—0.5OEM-T121-101———
2Wheel 1—W55—0.5OEM-T121-54———
3Analogue 10————————
4Digital 1————————
5Analogue 3—W36—0.5OEM-T121-33———
6Analogue 4—W37—0.5OEM-T121-84———
7Thermistor 1—W40—0.5OEM-T121-93———
8—————————
95v Output—W23—0.5SP-5V2-1———
10Analogue 1—W34—0.5OEM-T121-53———
11—————————
12Crank—W24—0.5OEM-T121-82———
13—————————
14Digital 4————————
15Digital 5————————
16Analogue 11————————
17Thermistor 3————————
18—————————
19Analogue 6—W38—0.5OEM-T121-35———
20—————————
21Sensor Ground—W15—0.5SP-0V-1———
22Cam 1—W25—0.5OEM-T121-86———
23—————————
245v Output—W19—0.5SP-5V1-1———
25Thermistor 2—W54—0.5OEM-T121-85———
26CAN High—W56—0.5OEM-T121-60———
27—————————
28CAN Low—W57—0.5OEM-T121-58———
29—————————
30—————————
31—————————
32—————————
33Sensor Ground—W16—0.5SP-0V-1———
34Analogue 9—W53—0.5OEM-T121-69———

T4-C3

Mating face
T4-C3-11T4-C3-22T4-C3-33T4-C3-44T4-C3-55T4-C3-66T4-C3-7 · Lambda 1 Pump Current7T4-C3-8 · Lambda 1 VGND8T4-C3-9 · Lambda 1 Heater Negative9T4-C3-10 · PWM 810T4-C3-11 · Lambda 1 Trim Resistor11T4-C3-12 · Lambda 1 Nernst Voltage12T4-C3-1313T4-C3-1414T4-C3-1515T4-C3-1616T4-C3-17 · Analogue 717T4-C3-18 · Analogue 818T4-C3-1919T4-C3-2020T4-C3-2121T4-C3-22 · PWM 422T4-C3-23 · PWM 523T4-C3-24 · PWM 624T4-C3-25 · PWM 725T4-C3-26 · Permanent 12v26T4-C3-27 · Permanent 12v27T4-C3-2828T4-C3-2929T4-C3-3030T4-C3-3131T4-C3-3232T4-C3-3333T4-C3-3434
Wire side
T4-C3-11T4-C3-22T4-C3-33T4-C3-44T4-C3-55T4-C3-66T4-C3-7 · Lambda 1 Pump Current7T4-C3-8 · Lambda 1 VGND8T4-C3-9 · Lambda 1 Heater Negative9T4-C3-10 · PWM 810T4-C3-11 · Lambda 1 Trim Resistor11T4-C3-12 · Lambda 1 Nernst Voltage12T4-C3-1313T4-C3-1414T4-C3-1515T4-C3-1616T4-C3-17 · Analogue 717T4-C3-18 · Analogue 818T4-C3-1919T4-C3-2020T4-C3-2121T4-C3-22 · PWM 422T4-C3-23 · PWM 523T4-C3-24 · PWM 624T4-C3-25 · PWM 725T4-C3-26 · Permanent 12v26T4-C3-27 · Permanent 12v27T4-C3-2828T4-C3-2929T4-C3-3030T4-C3-3131T4-C3-3232T4-C3-3333T4-C3-3434
CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1—————————
2—————————
3—————————
4—————————
5—————————
6—————————
7Lambda 1 Pump Current—W50—0.5OEM-T121-51———
8Lambda 1 VGND————————
9Lambda 1 Heater Negative—W43—0.5OEM-T121-5———
10PWM 8—W49—0.5OEM-T121-48———
11Lambda 1 Trim Resistor————————
12Lambda 1 Nernst Voltage—W51—0.5OEM-T121-70———
13—————————
14—————————
15—————————
16—————————
17Analogue 7—W39—0.5OEM-T121-92———
18Analogue 8—W52—0.5OEM-T121-68———
19—————————
20—————————
21—————————
22PWM 4—W45—0.5OEM-T121-104———
23PWM 5—W46—0.5OEM-T121-105———
24PWM 6—W47—0.5OEM-T121-115———
25PWM 7—W48—0.5OEM-T121-47———
26Permanent 12v—W4—0.85OEM-T121-62———
27Permanent 12v————————
28—————————
29—————————
30—————————
31—————————
32—————————
33—————————
34—————————

Pin map

OEM pointOEM functionOEM familyTarget pointTarget functionTarget familyWire colourEvidence
OEM-T121-1ECU groundgroundT4-C1-13 + T4-C1-14Power Ground 1 + Power Ground 2groundcorroborated
OEM-T121-101Boost pressure sensor (G31)analog_inT4-C2-1Analogue 2analog_incorroborated
OEM-T121-102Ignition coil 1 (N127)ignition_outT4-C1-10Coil 1ignition_outcorroborated
OEM-T121-103Ignition coil 3 (N158)ignition_outT4-C1-1Coil 3ignition_outcorroborated
OEM-T121-104Boost control solenoid (N75)low_side_outT4-C3-22PWM 4low_side_outcorroborated
OEM-T121-105Diverter valve (N249)low_side_outT4-C3-23PWM 5low_side_outcorroborated
OEM-T121-106Knock sensor 1 (G61)knock_in———corroborated
OEM-T121-107Knock sensor 2 (G66)knock_in———corroborated
OEM-T121-108Sensor groundsensor_groundT4-C2-21 + T4-C2-33Sensor Ground + Sensor Groundsensor_groundcorroborated
OEM-T121-115VVT camshaft adjustment valve (N205)low_side_outT4-C3-24PWM 6low_side_outcorroborated
OEM-T121-117Throttle motor G186 (+)hbridge_out———corroborated
OEM-T121-118Throttle motor G186 (−)hbridge_out———corroborated
OEM-T121-121ECM + coil power (J271 relay feed)power_inT4-C1-31Ignition 12v Inpower_incorroborated
OEM-T121-2ECU groundgroundT4-C1-13 + T4-C1-14Power Ground 1 + Power Ground 2groundcorroborated
OEM-T121-21ECM power (J271 relay feed)power_inT4-C1-31Ignition 12v Inpower_incorroborated
OEM-T121-27MAF sensor supply (G70)power_in———corroborated
OEM-T121-29MAF sensor ground (G70)sensor_groundT4-C2-21 + T4-C2-33Sensor Ground + Sensor Groundsensor_groundcorroborated
OEM-T121-3Ignition switch +12V (term 15)digital_in———corroborated
OEM-T121-33Accelerator pedal position 1 (G79)analog_inT4-C2-5Analogue 3analog_incorroborated
OEM-T121-34Accelerator pedal position 1 ground (G79)sensor_groundT4-C2-21 + T4-C2-33Sensor Ground + Sensor Groundsensor_groundcorroborated
OEM-T121-35Accelerator pedal position 2 (G185)analog_inT4-C2-19Analogue 6analog_incorroborated
OEM-T121-36Accelerator pedal position 2 ground (G185)sensor_groundT4-C2-21 + T4-C2-33Sensor Ground + Sensor Groundsensor_groundcorroborated
OEM-T121-37Engine speed signal (tacho to cluster)tacho_out———corroborated
OEM-T121-43K-line diagnostics (OBD pin 7)serial———corroborated
OEM-T121-47Check engine light (MIL)low_side_outT4-C3-25PWM 7low_side_outcorroborated
OEM-T121-48EPC warning lightlow_side_outT4-C3-10PWM 8low_side_outcorroborated
OEM-T121-5Wideband lambda heater (Z19)low_side_outT4-C3-9Lambda 1 Heater Negativelow_side_outcorroborated
OEM-T121-51Wideband lambda pump (G39)wb_ipT4-C3-7Lambda 1 Pump Currentwb_ipcorroborated
OEM-T121-52Wideband lambda pump (G39)wb_ip———corroborated
OEM-T121-53MAF sensor signal (G70)analog_inT4-C2-10Analogue 1analog_incorroborated
OEM-T121-54Road speed signal (VSS)digital_inT4-C2-2Wheel 1digital_incorroborated
OEM-T121-58CAN bus lowcan_lT4-C2-28CAN Lowcan_lcorroborated
OEM-T121-60CAN bus highcan_hT4-C2-26CAN Highcan_hcorroborated
OEM-T121-62Battery constant +12V (term 30)power_inT4-C3-26Permanent 12vpower_incorroborated
OEM-T121-63Post-cat lambda heater (Z29)low_side_outT4-C1-3PWM 3low_side_outcorroborated
OEM-T121-64EVAP canister valve (N80)low_side_out———corroborated
OEM-T121-65Fuel pump relay controllow_side_outT4-C1-5PWM 1low_side_outcorroborated
OEM-T121-66Secondary-air pump relay (J299)low_side_outT4-C1-4PWM 2low_side_outcorroborated
OEM-T121-68Post-cat lambda signal (G130)lambda_nb_inT4-C3-18Analogue 8analog_incorroborated
OEM-T121-69Post-cat lambda signal (G130)lambda_nb_inT4-C2-34Analogue 9analog_incorroborated
OEM-T121-70Wideband lambda Nernst signal (G39)wb_vsT4-C3-12Lambda 1 Nernst Voltagewb_vscorroborated
OEM-T121-71Wideband lambda Nernst signal (G39)wb_vs———corroborated
OEM-T121-72Accelerator pedal position 1 5V supply (G79)vrefT4-C2-245v Outputvrefcorroborated
OEM-T121-73Accelerator pedal position 2 5V supply (G185)vrefT4-C2-95v Outputvrefcorroborated
OEM-T121-82Crank position sensor (G28)trigger_inT4-C2-12Cranktrigger_incorroborated
OEM-T121-83Throttle position sensor 5V supply (G187/G188)vrefT4-C2-95v Outputvrefcorroborated
OEM-T121-84Throttle position sensor 1 (G187)analog_inT4-C2-6Analogue 4analog_incorroborated
OEM-T121-85Intake air temperature (G42)temp_inT4-C2-25Thermistor 2temp_incorroborated
OEM-T121-86Camshaft position sensor (G40)trigger_inT4-C2-22Cam 1trigger_incorroborated
OEM-T121-88Injector 4 (N33)injector_outT4-C1-25Injector 4injector_outcorroborated
OEM-T121-89Injector 2 (N31)injector_outT4-C1-17Injector 2injector_outcorroborated
OEM-T121-9Secondary-air injection valve (N112)low_side_out———corroborated
OEM-T121-90Crank position sensor ground (G28)sensor_groundT4-C2-21 + T4-C2-33Sensor Ground + Sensor Groundsensor_groundcorroborated
OEM-T121-91Throttle position sensor ground (G187/G188)sensor_groundT4-C2-21 + T4-C2-33Sensor Ground + Sensor Groundsensor_groundcorroborated
OEM-T121-92Throttle position sensor 2 (G188)analog_inT4-C3-17Analogue 7analog_incorroborated
OEM-T121-93Engine coolant temperature (G62)temp_inT4-C2-7Thermistor 1temp_incorroborated
OEM-T121-94Ignition coil 4 (N163)ignition_outT4-C1-26Coil 4ignition_outcorroborated
OEM-T121-95Ignition coil 2 (N128)ignition_outT4-C1-18Coil 2ignition_outcorroborated
OEM-T121-96Injector 1 (N30)injector_outT4-C1-9Injector 1injector_outcorroborated
OEM-T121-97Injector 3 (N32)injector_outT4-C1-34Injector 3injector_outcorroborated
OEM-T121-98Cam + boost sensor 5V supply (G40/G31)vrefT4-C2-245v Outputvrefcorroborated
OEM-T121-99Knock sensor 5V supply (G61/G66)vrefT4-C2-95v Outputvrefcorroborated

Cut list

WireFromToGauge (mm²)ColourLengthSignalIdent
W1OEM-T121-121SP-14V-10.85no routeECM + coil power (J271 relay feed)—
W2OEM-T121-21SP-14V-10.85no routeECM power (J271 relay feed)—
W3SP-14V-1T4-C1-310.85no routeIgnition 12v In—
W4OEM-T121-62T4-C3-260.85no routeBattery constant +12V (term 30)—
W5OEM-T121-1SP-GND-10.85no routeECU ground—
W6OEM-T121-2SP-GND-10.85no routeECU ground—
W7SP-GND-1T4-C1-130.85no routePower Ground 1—
W8SP-GND-1T4-C1-140.85no routePower Ground 2—
W9OEM-T121-108SP-0V-10.5no routeSensor ground—
W10OEM-T121-29SP-0V-10.5no routeMAF sensor ground (G70)—
W11OEM-T121-34SP-0V-10.5no routeAccelerator pedal position 1 ground (G79)—
W12OEM-T121-36SP-0V-10.5no routeAccelerator pedal position 2 ground (G185)—
W13OEM-T121-90SP-0V-10.5no routeCrank position sensor ground (G28)—
W14OEM-T121-91SP-0V-10.5no routeThrottle position sensor ground (G187/G188)—
W15SP-0V-1T4-C2-210.5no routeSensor Ground—
W16SP-0V-1T4-C2-330.5no routeSensor Ground—
W17OEM-T121-72SP-5V1-10.5no routeAccelerator pedal position 1 5V supply (G79)—
W18OEM-T121-98SP-5V1-10.5no routeCam + boost sensor 5V supply (G40/G31)—
W19SP-5V1-1T4-C2-240.5no route5v Output—
W20OEM-T121-73SP-5V2-10.5no routeAccelerator pedal position 2 5V supply (G185)—
W21OEM-T121-83SP-5V2-10.5no routeThrottle position sensor 5V supply (G187/G188)—
W22OEM-T121-99SP-5V2-10.5no routeKnock sensor 5V supply (G61/G66)—
W23SP-5V2-1T4-C2-90.5no route5v Output—
W24OEM-T121-82T4-C2-120.5no routeCrank position sensor (G28)—
W25OEM-T121-86T4-C2-220.5no routeCamshaft position sensor (G40)—
W26OEM-T121-102T4-C1-100.5no routeIgnition coil 1 (N127)—
W27OEM-T121-95T4-C1-180.5no routeIgnition coil 2 (N128)—
W28OEM-T121-103T4-C1-10.5no routeIgnition coil 3 (N158)—
W29OEM-T121-94T4-C1-260.5no routeIgnition coil 4 (N163)—
W30OEM-T121-96T4-C1-90.5no routeInjector 1 (N30)—
W31OEM-T121-89T4-C1-170.5no routeInjector 2 (N31)—
W32OEM-T121-97T4-C1-340.5no routeInjector 3 (N32)—
W33OEM-T121-88T4-C1-250.5no routeInjector 4 (N33)—
W34OEM-T121-53T4-C2-100.5no routeMAF sensor signal (G70)—
W35OEM-T121-101T4-C2-10.5no routeBoost pressure sensor (G31)—
W36OEM-T121-33T4-C2-50.5no routeAccelerator pedal position 1 (G79)—
W37OEM-T121-84T4-C2-60.5no routeThrottle position sensor 1 (G187)—
W38OEM-T121-35T4-C2-190.5no routeAccelerator pedal position 2 (G185)—
W39OEM-T121-92T4-C3-170.5no routeThrottle position sensor 2 (G188)—
W40OEM-T121-93T4-C2-70.5no routeEngine coolant temperature (G62)—
W41OEM-T121-65T4-C1-50.5no routeFuel pump relay control—
W42OEM-T121-66T4-C1-40.5no routeSecondary-air pump relay (J299)—
W43OEM-T121-5T4-C3-90.5no routeWideband lambda heater (Z19)—
W44OEM-T121-63T4-C1-30.5no routePost-cat lambda heater (Z29)—
W45OEM-T121-104T4-C3-220.5no routeBoost control solenoid (N75)—
W46OEM-T121-105T4-C3-230.5no routeDiverter valve (N249)—
W47OEM-T121-115T4-C3-240.5no routeVVT camshaft adjustment valve (N205)—
W48OEM-T121-47T4-C3-250.5no routeCheck engine light (MIL)—
W49OEM-T121-48T4-C3-100.5no routeEPC warning light—
W50OEM-T121-51T4-C3-70.5no routeWideband lambda pump (G39)—
W51OEM-T121-70T4-C3-120.5no routeWideband lambda Nernst signal (G39)—
W52OEM-T121-68T4-C3-180.5no routePost-cat lambda signal (G130)—
W53OEM-T121-69T4-C2-340.5no routePost-cat lambda signal (G130)—
W54OEM-T121-85T4-C2-250.5no routeIntake air temperature (G42)—
W55OEM-T121-54T4-C2-20.5no routeRoad speed signal (VSS)—
W56OEM-T121-60T4-C2-260.5no routeCAN bus high—
W57OEM-T121-58T4-C2-280.5no routeCAN bus low—

Bill of materials

CategoryPart numberManufacturerDescriptionQtyUnit
connector4-1437290-0TESuperseal 1.0 34-way plug, Key 13.000ea
terminal3-1447221-4TESuperseal 1.0 socket terminal, 20 AWG (0.5 sq mm)42.000ea

ECU setup sheet

RoleEngine refEngine signalSensorECU pointECU functionECU classSetup flag
No configured channels.

Findings

Open (14)

SeverityCodeSubjectMessage
errorPHYS_REQUIRED_OPENT4-C3-27T4-C3-27 "Permanent 12v" is required but not wired.
errorREQUIRED_UNMAPPEDOEM-T121-106Required OEM function "Knock sensor 1 (G61)" (knock_in) is not connected to the new ECU.
errorREQUIRED_UNMAPPEDOEM-T121-107Required OEM function "Knock sensor 2 (G66)" (knock_in) is not connected to the new ECU.
errorREQUIRED_UNMAPPEDOEM-T121-117Required OEM function "Throttle motor G186 (+)" (hbridge_out) is not connected to the new ECU.
errorREQUIRED_UNMAPPEDOEM-T121-118Required OEM function "Throttle motor G186 (−)" (hbridge_out) is not connected to the new ECU.
errorREQUIRED_UNMAPPEDOEM-T121-3Required OEM function "Ignition switch +12V (term 15)" (digital_in) is not connected to the new ECU.
warnDATASET_GAPT4 C120 of 34 cavities on T4 C1 have no pin data (2,6,7,8,11,12,15,16,19,20,21,22,23,24,27,28,29,30,32,33). Anything there is invisible to these checks.
warnDATASET_GAPT4 C211 of 34 cavities on T4 C2 have no pin data (8,11,13,18,20,23,27,29,30,31,32). Anything there is invisible to these checks.
warnDATASET_GAPT4 C320 of 34 cavities on T4 C3 have no pin data (1,2,3,4,5,6,13,14,15,16,19,20,21,28,29,30,31,32,33,34). Anything there is invisible to these checks.
warnDBW_SHARED_5VOEM-T121-72 + OEM-T121-98 + SP-5V1-1 + T4-C2-24These 5 V supplies are separate in the stock car (OEM-T121-72 [pedal1], OEM-T121-98 [cam_boost]) and here share one ECU 5 V (T4-C2-24). On a drive-by-wire car the OEM splits them so one short or fault can't corrupt both throttle/pedal tracks at once. T4 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.
warnDBW_SHARED_5VOEM-T121-73 + OEM-T121-83 + OEM-T121-99 + SP-5V2-1 + T4-C2-9These 5 V supplies are separate in the stock car (OEM-T121-73 [pedal2], OEM-T121-83 [tps], OEM-T121-99 [knock]) and here share one ECU 5 V (T4-C2-9). On a drive-by-wire car the OEM splits them so one short or fault can't corrupt both throttle/pedal tracks at once. T4 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.
warnSUPPLY_GROUPOEM-T121-72 + OEM-T121-98 + SP-5V1-1 + T4-C2-24Supplies meant to stay independent share one net: OEM-T121-72 [pedal1], 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.
warnSUPPLY_GROUPOEM-T121-73 + OEM-T121-83 + OEM-T121-99 + SP-5V2-1 + T4-C2-9Supplies meant to stay independent share one net: OEM-T121-73 [pedal2], 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.
infoUNMAPPEDOEM7 optional OEM pins are not mapped: OEM-T121-27 MAF sensor supply (G70); OEM-T121-37 Engine speed signal (tacho to cluster); OEM-T121-43 K-line diagnostics (OBD pin 7); OEM-T121-52 Wideband lambda pump (G39); OEM-T121-64 EVAP canister valve (N80); OEM-T121-71 Wideband lambda Nernst signal (G39); OEM-T121-9 Secondary-air injection valve (N112)

Accepted (0)

CodeSubjectReasonBy

Notes

Fit check: needs add-on. Resolve these before building: - No drive-by-wire; needs a cable-throttle conversion or an external DBW controller - 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: - OEM-T121 106: Knock sensor 1 (G61): no free knock input on DTAFast T4 - OEM-T121 107: Knock sensor 2 (G66): no free knock input on DTAFast T4 - OEM-T121 117: Throttle motor G186 (+): needs a paired H-bridge on DTAFast T4 (H-bridge pairing not in the library: set device_pin.bridge_pair from the ECU manual) - OEM-T121 118: Throttle motor G186 (−): needs a paired H-bridge on DTAFast T4 (H-bridge pairing not in the library: set device_pin.bridge_pair from the ECU manual) - 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); DTAFast T4 has no dedicated key-on input - T4-C3 27: Permanent 12v: required by DTAFast T4 but no stock pin feeds it; wire by hand Not wired: - OEM-T121 64: EVAP canister valve (N80): no free low_side/relay_control/heater_low_side/ls_hs/injector on DTAFast T4 - OEM-T121 9: Secondary-air injection valve (N112): no free low_side/relay_control/heater_low_side/ls_hs/injector on DTAFast T4 - OEM-T121 37: Engine speed signal (tacho to cluster): no free tacho/frequency_out/low_side/ls_hs on DTAFast T4 - OEM-T121 52: Wideband lambda pump (G39): no free wb_ip on DTAFast T4 - OEM-T121 71: Wideband lambda Nernst signal (G39): no free wb_vs on DTAFast T4 - OEM-T121 43: K-line diagnostics (OBD pin 7): no free k_line on DTAFast T4 - OEM-T121 27: MAF sensor supply (G70): no rule for class sensor_supply_in; wire by hand

Sources

ReliabilityKindTitleURLArchiveCapturedSHA-256
4vendor_docDTAFast T4 ECU wiring diagramhttps://cdn.shopify.com/s/files/1/0848/7508/4108/files/T4_Wiring_Diagram.pdf?v=1789413067———
3community_copyNefMoto: ME7.5 ECU bench-flashing power/ground pinshttp://nefmoto.com/wiki/index.php?title=ECU_Bench_Flashing———
3community_copyvwressources: Bosch Motronic ME7.5 (AMK/ARY/AUQ/ARX/AUM) T121 pinouthttps://www.vwressources.planethoster.world/me75_pinout.html———