Understanding the Obd1 Ecu Pinout is crucial for diagnosing and modifying Honda vehicles from the early 1990s. This guide provides detailed pinout diagrams and explanations for both OBD0 and OBD1 Honda ECUs, covering popular models like the Civic, CRX, and Integra. Knowing these pinouts allows you to troubleshoot engine issues, install aftermarket performance parts, and gain a deeper understanding of your Honda’s engine management system.
OBD0 ECU Pinout (1988-1991 Honda Civic/CRX SI, 90-91 Integra)
OBD0 systems utilized three connectors: A, B, and C.
Connector A
This connector manages core engine functions:
- Pins 1-7: Injector controls (injectors 1-4, colors vary)
- Pins 2 & 4: Main relay ground
- Pin 6: Purge cut-off solenoid valve
- Pin 11: Electronic Air Control/Idle Air Control Valve (EAC/IACV)
- Pins 12-15: Main relay and injector resistor box connections
- Pins 16 & 18: Ground connections
Connector B
This connector handles auxiliary controls and sensors:
- Pin 1: Hazard fuse
- Pin 2: Fast idle control valve
- Pin 3: A/C clutch relay
- Pins 4 & 10: Crank angle sensor
- Pin 5: Alternator
- Pin 6: Check engine light
- Pin 8: A/C switch
- Pin 12: Crank angle sensor
- Pin 13: Main relay
- Pin 14: Alternator
- Pins 15 & 17: Igniter unit
- Pin 16: Speed sensor
- Pin 19: Electric load detector
- Pin 20: Ignition timing adjusting connector
Connector C
This connector focuses on critical sensor inputs:
- Pins 1 & 2: Cylinder position sensor
- Pins 3 & 4: Top Dead Center (TDC) sensor
- Pin 5: Intake Air Temperature (IAT) sensor
- Pin 6: Engine Coolant Temperature (ECT) sensor
- Pin 7: Throttle Position Sensor (TPS)
- Pin 9: Manifold Absolute Pressure (MAP) sensor
- Pin 10: Brake switch
- Pin 11: MAP sensor
- Pin 12: Sensor voltage and ground
- Pins 13-15: MAP sensor
- Pin 16: Oxygen sensor (O2 sensor)
OBD1 ECU Pinout (1992-1995 Honda Civic/Integra)
OBD1 systems simplified to connectors A, B, and D. Pinouts vary slightly between Civic and Integra models. Refer to a model-specific diagram for precise information.
Connector A (OBD1)
- Similar to OBD0 Connector A, but with additions for OBD1 features like VTEC, EGR, and more sophisticated diagnostics.
Connector B (OBD1)
- Includes inputs for critical sensors like the Vehicle Speed Sensor (VSS), Crank Position Sensor (CKP), and Top Dead Center (TDC) sensor.
Connector D (OBD1)
- Houses connections for various sensors including Knock Sensor, O2 sensor, MAP sensor, TPS, and ECT sensor, as well as diagnostic communication lines (TXD/RXD).
Utilizing these OBD1 ECU pinout diagrams empowers Honda enthusiasts to effectively diagnose, modify, and understand their vehicle’s engine management system. Remember to consult a model-specific wiring diagram for the most accurate information.
