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VW Golf/Jetta Mk2 1.8 8v Digifant II → Haltech Nexus S3 HT-213000 (auto)

VW Golf/Jetta Mk2 1.8 8v Digifant II — Haltech — Nexus S3
⚠ 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.

Statusdraft · not yet verified: nobody has reported building and running this harness
Open errors1: read the Findings page before cutting any wire
Size of the job26 wires · 6 connectors · 0 part lines
ToolsCrimp and extraction tools for each terminal family (see Connectors) · wire strippers · multimeter · heat gun + heat-shrink
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-A-14SP-14V-10.85☐☐☐☐☐☐☐
W2SP-14V-1NEXUSS3-A-180.85☐☐☐☐☐☐☐
W3SP-14V-1NEXUSS3-A-250.85☐☐☐☐☐☐☐
W4OEM-A-13SP-GND-10.85☐☐☐☐☐☐☐
W5OEM-A-19SP-GND-10.85☐☐☐☐☐☐☐
W6SP-GND-1NEXUSS3-A-100.85☐☐☐☐☐☐☐
W7SP-GND-1NEXUSS3-A-110.85☐☐☐☐☐☐☐
W8OEM-A-5SP-0V-10.5☐☐☐☐☐☐☐
W9OEM-A-6SP-0V-10.5☐☐☐☐☐☐☐
W10SP-0V-1NEXUSS3-C-260.5☐☐☐☐☐☐☐
W11OEM-A-17NEXUSS3-C-250.5☐☐☐☐☐☐☐
W12OEM-A-18NEXUSS3-C-30.5☐☐☐☐☐☐☐
W13SP-0V-1NEXUSS3-C-40.5☐☐☐☐☐☐☐
W14OEM-A-4NEXUSS3-C-230.5☐☐☐☐☐☐☐
W15OEM-A-25NEXUSS3-A-270.5☐☐☐☐☐☐☐
W16OEM-A-12NEXUSS3-A-10.5☐☐☐☐☐☐☐
W17OEM-A-3NEXUSS3-A-260.5☐☐☐☐☐☐☐
W18OEM-A-21NEXUSS3-C-100.5☐☐☐☐☐☐☐
W19OEM-A-10NEXUSS3-C-110.5☐☐☐☐☐☐☐
W20OEM-A-22NEXUSS3-A-90.5☐☐☐☐☐☐☐
W21OEM-A-23NEXUSS3-A-120.5☐☐☐☐☐☐☐
W22OEM-A-2NEXUSS3-C-120.5☐☐☐☐☐☐☐
W23OEM-A-9NEXUSS3-C-130.5☐☐☐☐☐☐☐
W24OEM-A-1NEXUSS3-C-50.5☐☐☐☐☐☐☐
W25OEM-A-11NEXUSS3-C-60.5☐☐☐☐☐☐☐
W26OEM-A-16NEXUSS3-C-70.5☐☐☐☐☐☐☐

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
1NEXUSS3-A-18NEXUSS3-C-26open (OL)+12 V supply must not touch sensor ground
2NEXUSS3-C-25NEXUSS3-C-26open (OL)5 V sensor reference must not touch sensor ground
3NEXUSS3-A-10NEXUSS3-A-18open (OL)power ground must not touch +12 V supply
4NEXUSS3-A-10NEXUSS3-C-25open (OL)power ground must not touch 5 V sensor reference
5NEXUSS3-A-18NEXUSS3-C-25open (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

NEXUSS3-ANEXUSS3-COEM-ASP-0VSP-14VSP-GND

Connectors

NEXUSS3-A

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1Injector 1—W16—0.5OEM-A-12———
10Battery ground—W6—0.85SP-GND-1———
11Battery ground—W7—0.85SP-GND-1———
12DPO 2—W21—0.5OEM-A-23———
13Ignition switch input————————
14DPO 3————————
15DPO 4————————
16DPO 5————————
17DPO 6————————
18+12V switched input—W2—0.85SP-14V-1———
19HBO 1————————
2Injector 2————————
20HBO 2————————
21HBO 3————————
22HBO 4————————
23CAN 1 High————————
24CAN 1 Low————————
25+12V switched input—W3—0.85SP-14V-1———
26ECR output—W17—0.5OEM-A-3———
27Ignition 1—W15—0.5OEM-A-25———
28Ignition 2————————
29Ignition 3————————
3Injector 3————————
30Ignition 4————————
31Ignition 5————————
32Ignition 6————————
33Ignition 7————————
34Ignition 8————————
4Injector 4————————
5Injector 5————————
6Injector 6————————
7Injector 7————————
8Injector 8————————
9DPO 1—W20—0.5OEM-A-22———

NEXUSS3-C

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1Trigger +————————
10AVI 1—W18—0.5OEM-A-21———
11AVI 2—W19—0.5OEM-A-10———
12AVI 3—W22—0.5OEM-A-2———
13AVI 4—W23—0.5OEM-A-9———
14AVI 5————————
15AVI 6————————
16AVI 7————————
17AVI 8————————
18AVI 9————————
19SPI 5————————
2Trigger -————————
20SPI 6————————
21CAN 2 High————————
22CAN 2 Low————————
23Knock 1—W14—0.5OEM-A-4———
24Knock 2————————
25+5V—W11—0.5OEM-A-17———
26Signal ground—W10—0.5SP-0V-1———
27AVI 10————————
28AVI 11————————
29WBI 1 Heater +————————
3Home +—W12—0.5OEM-A-18———
30WBI 1 Input————————
31WBI 1 Pump————————
32WBI 1 Nernst————————
33WBI 1 Heater -————————
34WBI 1 Cal————————
4Home -—W13—0.5SP-0V-1———
5SPI 1—W24—0.5OEM-A-1———
6SPI 2—W25—0.5OEM-A-11———
7SPI 3—W26—0.5OEM-A-16———
8SPI 4————————
9+8V————————

OEM-A

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1Starter signal (term 50)—W24—0.5NEXUSS3-C-5———
10Coolant temperature sensor—W19—0.5NEXUSS3-C-11———
11Idle/WOT throttle switch—W25—0.5NEXUSS3-C-6———
12Injector driver (batch, all 4)—W16—0.5NEXUSS3-A-1———
13Ground—W4—0.85SP-GND-1———
14ECU power (control-unit relay)—W1—0.85SP-14V-1———
16A/C compressor signal—W26—0.5NEXUSS3-C-7———
17AFM potentiometer supply—W11—0.5NEXUSS3-C-25———
18Hall sender signal (engine speed)—W12—0.5NEXUSS3-C-3———
19Ground—W5—0.85SP-GND-1———
2Oxygen (lambda) sensor signal—W22—0.5NEXUSS3-C-12———
21AFM signal—W18—0.5NEXUSS3-C-10———
22Idle stabilizer valve coil 1—W20—0.5NEXUSS3-A-9———
23Idle stabilizer valve coil 2—W21—0.5NEXUSS3-A-12———
25Ignition timing signal to TCI—W15—0.5NEXUSS3-A-27———
3Fuel pump relay control—W17—0.5NEXUSS3-A-26———
4Knock sensor signal—W14—0.5NEXUSS3-C-23———
5Knock sensor return—W8—0.5SP-0V-1———
6Sensor ground (CTS/Hall/AFM/throttle)—W9—0.5SP-0V-1———
7Knock sensor shield————————
8Hall sender supply (distributor)————————
9Intake air temperature sensor—W23—0.5NEXUSS3-C-13———

SP-0V

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W8—0.5OEM-A-5———
1——W9—0.5OEM-A-6———
1——W10—0.5NEXUSS3-C-26———
1——W13—0.5NEXUSS3-C-4———

SP-14V

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W1—0.85OEM-A-14———
1——W2—0.85NEXUSS3-A-18———
1——W3—0.85NEXUSS3-A-25———

SP-GND

CavityFunctionSignalWireColourGauge (mm²)DestinationTerminalSealPlug
1——W4—0.85OEM-A-13———
1——W5—0.85OEM-A-19———
1——W6—0.85NEXUSS3-A-10———
1——W7—0.85NEXUSS3-A-11———

Pin map

OEM pointOEM functionOEM familyTarget pointTarget functionTarget familyWire colourEvidence
OEM-A-1Starter signal (term 50)digital_inNEXUSS3-C-5SPI 1digital_incorroborated
OEM-A-10Coolant temperature sensortemp_inNEXUSS3-C-11AVI 2analog_incorroborated
OEM-A-11Idle/WOT throttle switchdigital_inNEXUSS3-C-6SPI 2digital_incorroborated
OEM-A-12Injector driver (batch, all 4)injector_outNEXUSS3-A-1Injector 1injector_outcorroborated
OEM-A-13GroundgroundNEXUSS3-A-10 + NEXUSS3-A-11Battery ground + Battery groundgroundcorroborated
OEM-A-14ECU power (control-unit relay)power_inNEXUSS3-A-18 + NEXUSS3-A-25+12V switched input + +12V switched inputpower_incorroborated
OEM-A-16A/C compressor signaldigital_inNEXUSS3-C-7SPI 3digital_incorroborated
OEM-A-17AFM potentiometer supplyvrefNEXUSS3-C-25+5Vvrefcorroborated
OEM-A-18Hall sender signal (engine speed)trigger_inNEXUSS3-C-3Home +trigger_incorroborated
OEM-A-19GroundgroundNEXUSS3-A-10 + NEXUSS3-A-11Battery ground + Battery groundgroundcorroborated
OEM-A-2Oxygen (lambda) sensor signallambda_nb_inNEXUSS3-C-12AVI 3analog_incorroborated
OEM-A-21AFM signalanalog_inNEXUSS3-C-10AVI 1analog_incorroborated
OEM-A-22Idle stabilizer valve coil 1low_side_outNEXUSS3-A-9DPO 1low_side_outcorroborated
OEM-A-23Idle stabilizer valve coil 2low_side_outNEXUSS3-A-12DPO 2low_side_outcorroborated
OEM-A-25Ignition timing signal to TCIignition_outNEXUSS3-A-27Ignition 1ignition_outcorroborated
OEM-A-3Fuel pump relay controllow_side_outNEXUSS3-A-26ECR outputlow_side_outcorroborated
OEM-A-4Knock sensor signalknock_inNEXUSS3-C-23Knock 1knock_incorroborated
OEM-A-5Knock sensor returnsensor_groundNEXUSS3-C-26 + NEXUSS3-C-4Signal ground + Home -sensor_ground + trigger_incorroborated
OEM-A-6Sensor ground (CTS/Hall/AFM/throttle)sensor_groundNEXUSS3-C-26 + NEXUSS3-C-4Signal ground + Home -sensor_ground + trigger_incorroborated
OEM-A-7Knock sensor shieldshield———corroborated
OEM-A-8Hall sender supply (distributor)power_in———corroborated
OEM-A-9Intake air temperature sensortemp_inNEXUSS3-C-13AVI 4analog_incorroborated

Cut list

WireFromToGauge (mm²)ColourLengthSignalIdent
W1OEM-A-14SP-14V-10.85no routeECU power (control-unit relay)—
W2SP-14V-1NEXUSS3-A-180.85no route+12V switched input—
W3SP-14V-1NEXUSS3-A-250.85no route+12V switched input—
W4OEM-A-13SP-GND-10.85no routeGround—
W5OEM-A-19SP-GND-10.85no routeGround—
W6SP-GND-1NEXUSS3-A-100.85no routeBattery ground—
W7SP-GND-1NEXUSS3-A-110.85no routeBattery ground—
W8OEM-A-5SP-0V-10.5no routeKnock sensor return—
W9OEM-A-6SP-0V-10.5no routeSensor ground (CTS/Hall/AFM/throttle)—
W10SP-0V-1NEXUSS3-C-260.5no routeSignal ground—
W11OEM-A-17NEXUSS3-C-250.5no routeAFM potentiometer supply—
W12OEM-A-18NEXUSS3-C-30.5no routeHall sender signal (engine speed)—
W13SP-0V-1NEXUSS3-C-40.5no routeHome -—
W14OEM-A-4NEXUSS3-C-230.5no routeKnock sensor signal—
W15OEM-A-25NEXUSS3-A-270.5no routeIgnition timing signal to TCI—
W16OEM-A-12NEXUSS3-A-10.5no routeInjector driver (batch, all 4)—
W17OEM-A-3NEXUSS3-A-260.5no routeFuel pump relay control—
W18OEM-A-21NEXUSS3-C-100.5no routeAFM signal—
W19OEM-A-10NEXUSS3-C-110.5no routeCoolant temperature sensor—
W20OEM-A-22NEXUSS3-A-90.5no routeIdle stabilizer valve coil 1—
W21OEM-A-23NEXUSS3-A-120.5no routeIdle stabilizer valve coil 2—
W22OEM-A-2NEXUSS3-C-120.5no routeOxygen (lambda) sensor signal—
W23OEM-A-9NEXUSS3-C-130.5no routeIntake air temperature sensor—
W24OEM-A-1NEXUSS3-C-50.5no routeStarter signal (term 50)—
W25OEM-A-11NEXUSS3-C-60.5no routeIdle/WOT throttle switch—
W26OEM-A-16NEXUSS3-C-70.5no routeA/C compressor signal—

Bill of materials

CategoryPart numberManufacturerDescriptionQtyUnit

ECU setup sheet

RoleEngine refEngine signalSensorECU pointECU functionECU classSetup flag
No configured channels.

Findings

Open (6)

SeverityCodeSubjectMessage
errorREQUIRED_UNMAPPEDOEM-A-8Required OEM function "Hall sender supply (distributor)" (power_in) is not connected to the new ECU.
warnLOAD_UNKNOWNNEXUSS3-A-26NEXUSS3-A-26 "ECR output" drives OEM-A-3 Fuel pump relay control (load 0.2 A) but its current rating is unknown. Check the ECU manual.
infoNET_FAMILYNEXUSS3-C-26 ↔ NEXUSS3-C-4NEXUSS3-C-26 "Signal 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.
infoNET_FAMILYOEM-A-10 ↔ NEXUSS3-C-11OEM-A-10 "Coolant temperature sensor" [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.
infoNET_FAMILYOEM-A-9 ↔ NEXUSS3-C-13OEM-A-9 "Intake air temperature sensor" [temp_in] is wired to NEXUSS3-C-13 "AVI 4" [analog_in]. Thermistor on a plain analog input needs a pull-up; check the channel can enable one.
infoUNMAPPEDOEM1 optional OEM pins are not mapped: OEM-A-7 Knock sensor shield

Accepted (0)

CodeSubjectReasonBy

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: - OEM-A 8: Hall sender supply (distributor): no rule for class sensor_supply_in; wire by hand Not wired: - OEM-A 7: Knock sensor shield: no shield pin 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

ReliabilityKindTitleURLArchiveCapturedSHA-256
4vendor_docHaltech: Nexus S3 Plug 'n' Play adapter QSG (Subaru WRX/STI ADM, HT-186300) — ECU Connector A & C pinouthttps://www.haltech.com/product/ht-186300-nexus-s3-plug-n-play-adapter-harness/archive2026-10-053cab7cd337c2
4vendor_docHaltech: Nexus S3/S2 ECU Overview (QSG) — specificationshttps://store.haltech.com/product/ht-213000-nexus-s3-ecu-only/archive2026-10-05388299668207
2community_copya2resource: Digifant II engine controller pinout (VW Golf/Jetta Mk2 1.8 8v)http://www.a2resource.com/electrical/management/digifant2.html———
2community_copydrive2.ru: VW Golf Mk2 PF Digifant II ECU pinouthttps://www.drive2.ru/l/9886121———