ECU - Electronic Control Unit Connector.
The 1992–1995 Honda Civic uses Honda’s PGM-FI (Programmed Fuel Injection) Engine Control Module, fitted to the EG and EH chassis with D-series engines (D15B, D16Z6). The ECM is an OBD1-era unit using a multi-connector arrangement and retrieves stored diagnostic trouble codes via a two-pin service check connector and MIL blink codes rather than a standardised diagnostic port. The module is located above the passenger footwell and governs injector timing, ignition advance, idle air control, and — on VTEC-equipped variants — the VTEC solenoid valve. Honda P-series ECU part numbers (P06, P28, P30) correspond to engine variant and VTEC fitment.
Connector A
| Pin | name | Signal |
|---|---|---|
| A4 | VTEC Solenoid Valve | Analog |
| A21 | Ignition Control Module | RPM |
| A24 | Power Ground | Ground |
Connector B
| Pin | name | Signal |
|---|---|---|
| B10 | Vehicle Speed Sensor | Speed |
Connector D
| Pin | name | Signal |
|---|---|---|
| D1 | Voltage Back Up | Power |
| D2 | Brake Switch | Analog |
| D6 | VTEC Pressure Switch | Analog |
| D11 | Throttle Position Sensor | Analog |
| D13 | Engine Coolant Temperature Sensor | Analog |
| D14 | Primary O2 Sensor | Analog |
| D15 | Intake Air Temperature Sensor | Analog |
| D17 | MAP Sensor | Analog 0.32V @ -13.9 PSI 4.84V @ 10.94 PSI |
Notes
Connectors are read from the wire side (back of connector) with the locking tab at the top; this orientation determines pin numbering. VTEC-equipped engines (D16Z6 with P28 ECU) use connector A pin A4 for the solenoid valve output and D6 for the VTEC oil pressure switch input; non-VTEC variants (D15B, P06 ECU) leave these positions unpopulated. To reset stored DTCs, disconnect the negative battery terminal for at least 30 seconds or remove the ECM back-up fuse; note that this also clears idle learn data, requiring an idle relearn procedure afterwards.
Signals
- VTEC Solenoid Valve (A4) — output signal activating the VTEC oil control solenoid on D16Z6 engines; absent on non-VTEC variants
- Ignition Control Module (A21) — RPM pulse signal exchanged with the ignition control module for timing control
- Power Ground (A24) — chassis ground reference for the ECM
- Vehicle Speed Sensor (B10) — speed pulse input from the vehicle speed sensor
- Voltage Back Up (D1) — constant 12 V supply retaining ECM memory and stored DTCs when ignition is off
- Brake Switch (D2) — input indicating brake pedal application
- VTEC Pressure Switch (D6) — input confirming VTEC oil pressure has risen sufficiently; used by ECM to verify solenoid actuation
- Throttle Position Sensor (D11) — analogue voltage input indicating throttle plate angle
- Engine Coolant Temperature Sensor (D13) — analogue input used for fuel enrichment, idle control, and fan activation
- Primary O2 Sensor (D14) — exhaust oxygen sensor input used for closed-loop fuelling correction
- Intake Air Temperature Sensor (D15) — analogue input correcting fuel delivery for inlet air density
- MAP Sensor (D17) — manifold absolute pressure input; output voltage ranges from approximately 0.32 V at −13.9 PSI to 4.84 V at 10.94 PSI