Isuzu 4hl1-1 Ecu Pinout File
| Pin | Function | Wire Color (Typical) | Voltage/Logic | | :--- | :--- | :--- | :--- | | A-1 | Main Battery Positive (ECU Backup) | White/Red | 12V Constant | | A-2 | Main Battery Positive (Injector Driver) | White/Red | 12V Constant | | A-10 | Main Ground (Power stage) | Black/White | 0V | | A-11 | Main Ground (Power stage) | Black | 0V | | A-20 | Ignition Switch (IG SW) | Black/Yellow | 12V (Key ON) | | A-22 | Main Relay Control (ECU grounds to activate) | Light Green | Signal to relay coil |
Technician Tip: If the scan tool cannot connect, check pin A-20 for 12V with the key on. Many novices forget the ECU needs a separate ignition feed.
When troubleshooting using the pinout, follow this safe process: isuzu 4hl1-1 ecu pinout
Connector B handles communication and driver request signals.
| Pin | Function | Type | Notes | |-----|-------------------------------|-------------------|----------------------------------| | B01 | CAN High (J1939 / OBD) | Digital differential | 2.5–3.5V (active) | | B02 | CAN Low (J1939 / OBD) | Digital differential | 1.5–2.5V (active) | | B03 | Tachometer output | Open collector | 4 pulses/rev, pull-up to 12V | | B04 | Check Engine Lamp (MIL) | Ground switched | 0V when active | | B05 | Glow Plug relay control | Ground switched | Active during pre-heat | | B06 | Starter relay enable | Ground switched | Allows cranking | | B07 | A/C request input | +12V switched | A/C ON = 12V | | B08 | Brake switch input | +12V | Used for idle-up / cruise cancel | | B09 | Clutch switch input | +12V | Cruise control / gear change | | B10 | Cruise control main switch | +12V | Enable line | | B11 | Cruise control SET/COAST | Resistive ladder | Analog or ground pulse | | B12 | Cruise control RES/ACC | Resistive ladder | Analog or ground pulse | | B13 | Immobilizer transponder coil | Digital coded signal | Connects to antenna ring around key | | B14–B48 | Body builder / transmission interface | Various | (Park/neutral, reverse lamp, etc.) | | Pin | Function | Wire Color (Typical)
| Pin No. | Function | Description | | :--- | :--- | :--- | | 12 | CAN High (J1939) | Communication Bus High | | 13 | CAN Low (J1939) | Communication Bus Low | | 20 | Tachometer Output | Engine RPM Signal to Dash | | 25 | Check Engine Lamp | Ground trigger for MIL light | | 40 | Vehicle Speed Sensor | Input from Transmission |
| Pin | Signal | Description | |------|--------|-------------| | A1 | GND | Sensor ground | | A2 | EOP | Engine oil pressure switch | | A3 | ECT | Engine coolant temp sensor | | A4 | IAT | Intake air temp sensor | | A5 | BARO | Barometric pressure (in ECU) | | A6 | TPS1 | Throttle position sensor 1 | | A7 | TPS2 | Throttle position sensor 2 | | A8 | VNT | Turbo VNT actuator control | | A9 | CMP+ | Camshaft position sensor (Hall+) | | A10 | CMP- | Camshaft position sensor (Hall-) | | A11 | CKP+ | Crankshaft position sensor | | A12 | CKP- | Crankshaft position sensor | | A13 | EGRV | EGR valve position feedback | | A14 | EGRC | EGR valve control (PWM) | | A15 | +5V | 5V sensor reference | | A16 | GND | Power ground | | A17 | VPWR | ECU main relay power | | A18 | VPWR | ECU main relay power | | A19 | GND | Power ground | | A20 | GND | Power ground | | A21 | FRP | Fuel rail pressure sensor signal | | A22 | FRP_GND | Rail pressure sensor ground | | A23 | FRP_5V | Rail pressure sensor 5V | | A24 | SCV1 | Suction control valve 1 (fuel pump) | | A25 | SCV2 | Suction control valve 2 | | A26 | INJ1 | Injector cylinder 1 (high side) | | A27 | INJ2 | Injector cylinder 2 | | A28 | INJ3 | Injector cylinder 3 | | A29 | INJ4 | Injector cylinder 4 | | A30 | INJ_LO | Injector common low side | | A31 | VSS | Vehicle speed sensor input | | A32 | NEUTRAL | Neutral switch | | A33 | AC_REQ | A/C request | | A34 | FAN | Cooling fan relay control | | A35 | MIL | Check engine light | | A36 | TACH | Tachometer output | | A37 | WSV | Water separator valve | | A38 | GLOW | Glow plug relay control | | A39 | +BAT | Constant battery (keep alive) | | A40 | IGN_SW | Ignition switch (key-on) | | A41 | CAN_H | CAN bus high (OBD/J1939) | | A42 | CAN_L | CAN bus low | | A43 | K_LINE | Diagnostic K-line (ISO 9141) | | A44 | GND | Shield ground for sensors | | A45-48 | NC | Not connected (varies) | | Pin No
The 4HL1-1 uses a 4-cylinder, 4.8-liter turbocharged diesel engine producing between 130–190 HP depending on the tune. Its ECU controls:
Without the correct ECU pinout, the following become nearly impossible: