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1990 JEEP CHEROKEE XJ 4.0L

STRIPPED ENGINE HARNESS — RENIX MPI WIRING DIAGRAMS

Source: Factory Service Manual Section 8W • Renix ECU System • For standalone/swap harness builds

Use +/− controls to zoom • Click any label to trace a wire across all sheets
Sheet 1: Power Distribution & Relays
POWER DISTRIBUTION & RELAY CONTROL 1990 XJ 4.0L Renix MPI — FSM Section 8W Sheets 9,10,15,20,21,22 BATTERY + − A0 BATTERY POSITIVE BUS — 1 8RD / 2 4RD / 10 RD — 4-8 AWG 4 BK (to engine block) IGNITION SWITCH (On Steering Column) ACC RUN ─── 11 14YL START ── 33 14DG OFF 10 12RD 11 14YL 33 14DG → Starter Relay (SH 9) S11 via fuse 11 14YL to ECU B8 FUSE PANEL (RH Shock Tower) 10 — 18GN (Hot at all times) 11 — 14YL (Ign RUN/START) Splices to SH 1,2,3,4,10 10 RD FUEL PUMP RELAY (RH Shock Tower) 85: 11 YL (ign run) 86: F17 OR* → ECU A5 30: 10 14RD (batt+) 87: F22 14OR (output) coil 10 14RD F22 14OR (Injector Feed Bus) F17 16OR* → ECU A5 F22 — INJECTOR FEED BUS — 14OR / 14OR/BK Feeds: Injectors 1-6 (via ballast resistor), O2 Heat Relay, EGR Solenoid, Ignition Module ECU C1, D1 Injector Feed Sense BALLAST RESISTOR (Near Air Filter) IGNITION MODULE SH 19 — RH Shock Tower O2 HEAT RELAY SH 20 — RH Shock Tower B+ LATCH RELAY (RH Shock Tower) 85: F21 16PK → ECU B10 86: F20 16BK* → ECU A9 30: 10 16RD (batt+) 87: B+ Output 10 16RD B+ Latch Output to ECU power RENIX ECU (Under Dash, Right of Steering Column — SH 111) A5 B8 B10 A9 B7 C1 D1 F21 16PK F20 16BK* 10 RD → ECU B7 (constant batt+) ENGINE GROUND 99 BK — RH Rear of Engine Block NOTES — Power Flow: 1. Battery → Fuse Panel → IGN Switch 2. IGN RUN (11 YL) → ECU B8 + FP Relay 3. ECU latches B+ relay via B10/A9 4. ECU grounds FP relay via A5 5. F22 (OR) feeds injectors, ign module 6. Battery direct → ECU B7 (constant)
Sheet 2: Engine Sensors
ENGINE SENSORS 1990 XJ 4.0L Renix MPI — FSM Section 8W Sheet 23 (Sensors), Sheets 19-20 (CPS/Sync/O2) 5V REFERENCE — from ECU internal regulator F15 18BR — SENSOR GROUND BUS — to ECU D3 CRITICAL: Keep sensor ground separate from power grounds (B11/B12) THROTTLE POSITION SENSOR (TPS) (On Throttle Body) 5V Ref: F77 20GY Signal: F50 20YL/GN Ground: F15 18BR Voltage divider: 0.5V closed to ~4.5V wide open throttle F77 20GY → ECU C15 F50 20YL/GN → ECU C7 MAP SENSOR (Intake Manifold, or Firewall) 5V Ref: F2 18RD* Signal: F14 18VT Ground: F15 18BR* +Shld: F56 20BK Outputs 1-5V proportional to manifold vacuum/pressure F2 18RD* → ECU C14 F14 18VT → ECU C6 INLET AIR TEMP SENSOR (IAT) (Air Cleaner / Intake Tube) Signal: F7 18TN* Ground: F15 18BK (shared) Thermistor: ~3kΩ cold, ~300Ω hot F7 18TN* → ECU C8 ENGINE COOLANT TEMP (ECT) (Cylinder Head, Rear) Signal: F24 18TN Ground: F15 18BK (shared) Thermistor: ~10kΩ cold, ~200Ω hot F24 18TN → ECU C10 RENIX ECU — SENSOR INPUTS (Under Dash, Right of Steering Column) C15 C7 C8 C14 C6 C10 C1 C5 D9 5V ref TPS IAT 5V ref MAP ECT CPS Sync O2 CRANKSHAFT POSITION SENSOR (CPS) (Bellhousing, Driver Side) Signal: F52 18VT Return: F53 18WT 2-wire magnetic pickup ~1000 RPM: 0.5V AC signal F52 18VT → C1 F53 18WT → D1 SYNC SIGNAL (DISTRIBUTOR) (Hall Effect in Distributor) Signal: F65 18GY 7.1V: F66 18BL ECU supplies 7.1V to power Hall sensor via C16 (F66 BL) F65 GY → C5 F66 BL ← C16 (7.1V from ECU) OXYGEN SENSOR (UPSTREAM) (Exhaust Manifold — Single) Signal: F6 18GY Heater: via O2 Heat Relay 0.1V = lean, 0.9V = rich Heater powered by F22 relay F6 18GY → ECU D9 KNOCK SENSOR (Cylinder Block, Passenger Side) Signal: F55 18YL* Ground: F54 18VT* Piezoelectric sensor ECU retards timing on knock Signal → D16, Ground → D8 F55 YL* → D16 F54 VT* → D8 NOTES — Sensor Circuits: 1. TPS/MAP share 5V ref bus 2. IAT/ECT/TPS/MAP share F15 sensor ground bus → D3 3. CPS is 2-wire AC pickup 4. Sync gets 7.1V from ECU 5. O2 is single upstream only 6. Knock has separate ground 7. * = tracer stripe on wire ECU D3 Sensor Ground
Sheet 3: Fuel Injectors
FUEL INJECTORS 1990 XJ 4.0L Renix MPI — FSM Section 8W Sheet 24 (Injectors), Sheet 21 (Ballast Resistor) F22 14OR — INJECTOR FEED BUS — from Fuel Pump Relay (SH 1) BALLAST RESISTOR PACK (Near Air Filter — Limits inrush current to injectors) 3 resistors: 2 injectors per resistor (pairs: 1-3, 5-6, 2-4) Ballast output feeds all 6 injectors (F22 OR, reduced voltage) INJ #1 Cyl 1 F71 18LB F71 18LB → ECU B1 INJ #2 Cyl 5 F72 18LG F72 18LG → ECU A3 INJ #3 Cyl 3 F73 18TN F73 18TN → ECU A1 INJ #4 Cyl 6 F74 18YL F74 18YL → ECU A4 INJ #5 Cyl 2 F75 18WT F75 18WT → ECU B2 INJ #6 Cyl 4 F76 18BR F76 18BR → ECU A2 RENIX ECU — INJECTOR DRIVERS ECU grounds each injector individually to fire — Firing Order: 1-5-3-6-2-4 B1 A3 A1 A4 B2 A2 F22 OR also connects to ECU C1 (injector feed sense) and D1 (injector feed sense) INJECTOR WIRING SUMMARY: Inj 1 (Cyl 1): F71 18LB → ECU B1 Inj 2 (Cyl 5): F72 18LG → ECU A3 Inj 3 (Cyl 3): F73 18TN → ECU A1 Inj 4 (Cyl 6): F74 18YL → ECU A4 Inj 5 (Cyl 2): F75 18WT → ECU B2 Inj 6 (Cyl 4): F76 18BR → ECU A2 NOTES — Fuel Injection: 1. All injectors share F22 OR power feed 2. Ballast resistor limits inrush current 3. ECU switches ground side to fire 4. Firing order: 1-5-3-6-2-4 5. All 18 AWG wires on driver side 6. F22 feed sense at ECU C1 + D1
Sheet 4: Ignition & AIS Motor
IGNITION SYSTEM & AIS MOTOR 1990 XJ 4.0L Renix MPI — FSM Section 8W Sheets 11,19 (Ignition), Sheet 24 (AIS) ── IGNITION SYSTEM ── IGNITION MODULE (RH Shock Tower — Renix Unit) Power: F22 14OR (from FP Relay) Coil(+): feeds ignition coil Coil(-): switches coil ground Timing: F27 16OR from ECU D13 Module controls dwell & fires coil based on ECU timing signal F22 14OR F22 OR (from FP Relay — SH 1) IGNITION COIL (On Valve Cover) (+) from module (-) switched by module HV out to distributor cap coil(+) coil(-) DISTRIBUTOR (Rear of Engine) HV in from coil Cap → Rotor → Plug Wires Contains Sync sensor HV CPS (CRANK SENSOR) (Bellhousing, Driver Side) Signal: F52 18VT → ECU C1 Return: F53 18WT → ECU D1 2-wire magnetic pickup, ~0.5V AC F52 VT F53 WT SYNC SENSOR (Hall Effect — Inside Distributor) Signal: F65 18GY → ECU C5 Power: F66 18BL ← ECU C16 (7.1V) F65 GY F66 BL F27 16OR — ECU Timing Reference → Ign Module (D13) RENIX ECU — IGNITION CONTROL C1:CPS C5:Sync C16:7.1V D1:CPS Ret D13:Timing Out ── AIS MOTOR ── AUTOMATIC IDLE SPEED (AIS) MOTOR (4-Wire Bipolar Stepper — On Throttle Body) COIL A: F68 18RD/YL → ECU D16 COIL B: F69 18PK/BK → ECU B6 COIL C: F70 18GN/BK → ECU B5 COIL D: F67 18BK/YL → ECU B4 ECU pulses coils in sequence to step pintle valve open/closed, controlling F68 18RD/YL → D16 F69 18PK/BK → B6 F70 18GN/BK → B5 F67 18BK/YL → B4 RENIX ECU — AIS CONTROL D16:Coil A B6:Coil B B5:Coil C B4:Coil D IGNITION SYSTEM NOTES: 1. Renix does NOT use waste-spark or coil-on-plug 2. Single coil → distributor cap → 6 plug wires 3. ECU calculates timing from CPS + Sync + MAP 4. ECU sends timing signal (F27) to ign module 5. Ign module controls coil dwell & fires coil 6. Module is powered by F22 (injector feed bus) 7. CPS failure = no start (most common crank/no-start) 8. Sync failure = runs rough, possible no-start AIS MOTOR NOTES: 1. 4-wire bipolar stepper motor 2. Controls idle air bypass around throttle plate 3. ECU steps motor open/closed to set idle RPM 4. All 4 wires are 18 AWG 5. Motor on throttle body (integral bypass passage) 6. If AIS fails: idle too high or too low 7. Can clean passage without removing motor 8. ECU resets AIS position at key-off
Sheet 5: Charging & Starting Systems
CHARGING & STARTING SYSTEMS 1990 XJ 4.0L Renix MPI — FSM Section 8W Sheets 6 (Charging), 9-10 (Starting) ══════════════ CHARGING SYSTEM ══════════════ BATTERY + A0 4-8RD FUSIBLE LINK (At Battery Terminal) 2 12RD ALTERNATOR (Front of Engine, Belt-Driven) G BAT terminal: 2 12RD to Battery Field: internal Ground: engine block Renix ECU does NOT control field voltage G103 — Engine Block VOLT GAUGE (Instrument Cluster) Reads alternator output voltage 2 RD CHARGING NOTES: 1. Internal voltage regulator 2. No ECU control of field 3. Output: 13.5-14.5V running 4. Ground through engine block 5. ~90A output (varies by RPM) ══════════════ STARTING SYSTEM ══════════════ BATTERY + A0 BATTERY POSITIVE — 4-8 AWG RD IGNITION SWITCH (START Position) Input: 10 RD (battery) START: 33 14DG Momentary contact while cranking 10 RD NEUTRAL SAFETY SWITCH Auto Trans: Park/Neutral only Manual: Clutch depressed only Prevents crank in gear 33 DG STARTER RELAY (LH Fender, Near Battery) 85: 33 DG (coil+) 86: Ground 30: A0 RD (batt+) 87: output → solenoid coil 33 DG A0 RD chassis gnd STARTER SOLENOID (On Starter Motor) S terminal: from relay relay output A0 RD (direct from battery) STARTER MOTOR (Bellhousing, Driver Side) M heavy cable Engine Block Ground STARTING SEQUENCE: 1. Key to START → 33 DG energized 2. NSS passes signal (P/N or clutch) 3. Starter relay coil energizes 4. Relay connects batt to solenoid S 5. Solenoid engages pinion + closes main contacts → motor cranks 6. Release key → relay drops out
Sheet 6: Ground Distribution
GROUND DISTRIBUTION 1990 XJ 4.0L Renix MPI — FSM Section 8W Ground Paths & ECU Ground Strategy CRITICAL: Sensor ground (D3) MUST be kept SEPARATE from power grounds (B11/B12) — noise causes sensor errors BATTERY (−) Z0 — BATTERY NEGATIVE BUS — 4 BK — 4-8 AWG ENGINE BLOCK GROUND G100 (RH Rear of Block) Primary engine ground point — heavy gauge strap Z0 4BK FIREWALL GND G101 (LH Dash Panel Bolt) Z0 ALTERNATOR GND G103 (Case to Engine Block) via block ══════════ ECU GROUND CIRCUITS ══════════ RENIX ECU (Under Dash, Right of Steering Column) B11 B12 D3 A5 A9 ECU POWER GROUNDS (Heavy — to Engine Block G100) B11: 99 18BK — Power Ground #1 B12: 99 18BK — Power Ground #2 Both pins to same circuit 99 Dual pins for current capacity 99 BK 99 18BK → G100 Engine Block SENSOR GROUND (SEPARATE from power ground!) D3: F15 18BR — Sensor GND Bus Shared by: • TPS ground (F15 → throttle body) • MAP ground (F15/F56 → manifold) • IAT ground (F15 → air intake) • ECT ground (F15 → cylinder head) F15 BR ECU-CONTROLLED RELAY GROUNDS A5: F17 16OR* — Fuel Pump Relay GND A9: F20 16BK* — B+ Latch Relay GND A7: F86 GY/YL — O2 Heat Relay GND F17 OR* F20 BK* ECU switches ground to energize relay coils (low-side drive) KNOCK SENSOR GROUND D8: F54 18VT* — Dedicated ground Separate from sensor ground bus GROUND CIRCUIT SUMMARY ECU PIN CIRCUIT WIRE FUNCTION DESTINATION B11, B12 99 18 BK ECU Power Ground G100 Block D3 F15 18 BR Sensor Ground Bus Sensors A5 F17 16 OR* Fuel Pump Relay FP Relay 86 A9 F20 16 BK* B+ Latch Relay B+ Relay 86 D8 F54 18 VT* Knock Sensor Knock Sens
Sheet 7: ECU Pinout Summary
RENIX ECU CONNECTOR PINOUT — COMPLETE REFERENCE 1990 XJ 4.0L Renix MPI — Single Multi-Row Connector (Rows A, B, C, D) — Active Pins for Bare Harness ECU Location: Under dash, right of steering column · Connector: Single multi-row · Rows A(12) B(12) C(16) D(12) = 52 pins total ROW A — 12 Pins (A1–A12) A1 F73 18TN Injector 3 Driver (Cyl 3) A2 F76 18BR Injector 6 Driver (Cyl 4) A3 F72 18LG Injector 2 Driver (Cyl 5) A4 F74 18YL Injector 4 Driver (Cyl 6) A5 F17 16OR* Fuel Pump Relay Ground Control A7 F86 GY/YL O2 Heat Relay Ground Control A9 F20 16BK* B+ Latch Relay Ground Control A10 F19 16GN EGR Solenoid Control A6, A8, A11, A12 — Not used in bare harness ROW B — 12 Pins (B1–B12) B1 F71 18LB Injector 1 Driver (Cyl 1) B2 F75 18WT Injector 5 Driver (Cyl 2) B3 F68 18RD/YL AIS Motor Coil A B4 F67 18BK/YL AIS Motor Coil D B5 F70 18GN/BK AIS Motor Coil C B6 F69 18PK/BK AIS Motor Coil B B7 10 16RD Battery (+) Constant Power B8 11 14YL Ignition Run (+) Sense B10 F21 16PK B+ Latch Relay Coil (+) B11 99 18BK Power Ground #1 (Heavy) B12 99 18BK Power Ground #2 (Heavy) B9 — Not used in bare harness ROW C — 16 Pins (C1–C16) — Primary Signal Row C1 F52 18VT CPS Signal (Crankshaft) C3 88 16GN Start Signal (+) C4 34 20BK Start Signal (−) C5 F65 18GY Sync Signal (Distributor) C6 F14 18VT MAP Sensor Signal C7 F50 20YL/GN TPS Signal C8 F7 18TN* IAT Sensor Signal C10 F24 18TN ECT Sensor Signal C11 F22 16OR Injector Feed Sense #1 C14 F2 18RD* MAP 5V Reference Supply C15 F77 20GY TPS 5V Reference Supply C16 F66 18BL Sync 7.1V Power Supply C2, C9, C12, C13 — Not used in bare harness ROW D — 12 Pins (D1–D12) D1 F53 18WT CPS Return D3 F15 18BR Sensor Ground Bus D8 F54 18VT* Knock Sensor Ground D9 F6 18GY O2 Sensor Signal D10 F22 16OR Injector Feed Sense #2 D13 F27 16OR Timing Reference → Ign Module D16 F55 18YL* Knock Sensor Signal D2, D4-D7, D11, D12 — Not used in bare harness PINOUT NOTES & BUILD REFERENCE WIRE COLOR CODES: RD=Red OR=Orange YL=Yellow GN=Green BL=Blue PK=Pink BR=Brown TN=Tan GY=Gray BK=Black LG=Light Green LB=Light Blue WT=White VT=Violet * = tracer stripe (e.g. OR* = orange w/ stripe) / = two colors (e.g. RD/YL = red w/ yellow stripe) CRITICAL BUILD NOTES: 1. Sensor ground (D3) MUST stay separate from B11/B12 2. F22 OR connects to both C11 and D10 (feed sense) 3. B11+B12 are same circuit (99) — dual for capacity 4. EGR (A10) can be omitted on emissions-delete builds 5. O2 heat relay (A7) optional for cold-start tuning ACTIVE PIN COUNT: Row A: 8 active of 12 | Row B: 11 active of 12 | Row C: 12 active of 16 | Row D: 6 active of 12 Total: 37 active pins of 52 — For bare engine harness build, only these pins need wiring.
Wire Color Reference Key
BK = Black
BL = Blue
BR = Brown
GN = Green
GY = Gray
LB = Light Blue
LG = Light Green
OR = Orange
PK = Pink
RD = Red
TN = Tan
VT = Violet
WT = White
YL = Yellow
CONNECTOR & TERMINAL PARTS LIST

The 1990 XJ Renix ECU uses a single multi-row connector with 4 rows (A, B, C, D). This is a different connector than the 1997+ JTEC 3-connector setup.

Renix ECU Connector

Renix 4.0L MPI ECU Connector (Multi-Row)
Single connector body with rows A (12-pin), B (12-pin), C (16-pin), D (12-pin). Located on passenger-side firewall.
Rows A & B: 12 cavities each • Row C: 16 cavities • Row D: 12 cavities

Quick Reference — Bare Harness Wire Count

CategoryWires
Injectors (6)6
AIS Motor4
CPS (2-wire)2
Sync (signal + 7.1V)2
TPS (5V + sig + gnd)3
MAP (5V + sig + gnd)3
IAT (signal)1
ECT (signal)1
O2 Sensor (signal)1
Knock Sensor (ground)1
Sensor Ground1
Power (Batt + Ign)2
Power Grounds (B11, B12)2
B+ Latch (relay + gnd)2
Fuel Pump Relay gnd1
Injector Feed (C11, D10)2
18 AWG GXL Wire (assorted)~100 ft
All wire colors, circuit codes, and pin assignments per 1990 Jeep Cherokee XJ FSM Section 8W.
Renix ECU system — NOT compatible with 1991+ Chrysler/JTEC wiring.
Always verify against your specific vehicle before cutting or connecting any wires.