OBD1 Civic and Integra ECU Reference
Technical reference for OBD1 Honda Civic and Acura Integra ECU pinouts, sensor configurations, and diagnostic specifications.
This document provides technical specifications and reference data for OBD1-era Honda Civic and Acura Integra Engine Control Units (ECUs).
Overview
OBD1 ECUs were utilized in Honda and Acura vehicles from 1992 to 1995. These units manage fuel injection, ignition timing, and emissions systems based on inputs from various engine sensors.
Diagnostic Resources
For detailed troubleshooting and error code identification, use the following tool:
ECU Pinout Reference
The following table outlines the standard connector configuration for OBD1 ECUs.
| Connector | Pins | Function |
|---|---|---|
| Plug A | 26 | Power, Ground, Injectors, IACV |
| Plug B | 16 | Sensors, VTEC, EGR, O2 |
| Plug C | 22 | Sensors, Distributor, Communication |
Important
Always verify wire colors against the factory service manual for your specific chassis code before performing electrical modifications.
Common Sensor Wiring
When integrating aftermarket sensors or wideband controllers, refer to the standard wiring configurations below:
Technical Notes
- Grounding: Ensure all sensor grounds are terminated at the ECU chassis ground (Pin A24/A25) to prevent signal noise.
- Shielding: Use shielded wire for sensitive signals such as the Knock Sensor and O2 sensor inputs to maintain signal integrity.
Tip
Resistor color codes used during ECU hardware modifications are included below.
Resistor Color Code Reference
Use the color bands on through-hole resistors to identify their resistance value before installing ECU jumpers, pull-ups, voltage dividers, or sensor-scaling parts.
How to Read the Bands
| Resistor Type | Band 1 | Band 2 | Band 3 | Band 4 | Band 5 |
|---|---|---|---|---|---|
| 4-band | 1st digit | 2nd digit | Multiplier | Tolerance | - |
| 5-band | 1st digit | 2nd digit | 3rd digit | Multiplier | Tolerance |
Color Values
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | x1 | - |
| Brown | 1 | x10 | +/- 1% |
| Red | 2 | x100 | +/- 2% |
| Orange | 3 | x1,000 | - |
| Yellow | 4 | x10,000 | - |
| Green | 5 | x100,000 | +/- 0.5% |
| Blue | 6 | x1,000,000 | +/- 0.25% |
| Violet | 7 | x10,000,000 | +/- 0.1% |
| Gray | 8 | x100,000,000 | +/- 0.05% |
| White | 9 | x1,000,000,000 | - |
| Gold | - | x0.1 | +/- 5% |
| Silver | - | x0.01 | +/- 10% |
| No band | - | - | +/- 20% |
Common ECU Examples
| Value | 4-Band Code | Typical Use |
|---|---|---|
| 220 ohm | Red, Red, Brown, Gold | LED/current-limiting or ECU hardware mods |
| 1k ohm | Brown, Black, Red, Gold | Pull-up, jumper, and driver-bias circuits |
| 1.2k ohm | Brown, Red, Red, Gold | Driver-bias circuits such as IACV repair references |
| 4.7k ohm | Yellow, Violet, Red, Gold | Transistor base resistor circuits |
| 10k ohm | Brown, Black, Orange, Gold | Pull-up, pull-down, and sensor-divider circuits |
Tip
Always confirm the measured value with a multimeter before soldering. Old ECU resistors can be heat-discolored, and some boards use small surface-mount parts marked with numeric codes instead of color bands.