ECU - Electronic Control Unit Connector.
The 1996–1998 Honda Civic (EK chassis) uses an OBD2 Engine Control Module (ECM/PCM) that manages the PGM-FI multi-point fuel injection system, ignition timing, idle air control, and — on VTEC-equipped variants — the VTEC solenoid valve. The ECM communicates with sensors including the MAP, throttle position, engine coolant temperature, intake air temperature, and primary and secondary oxygen sensors. Engines covered include the D16Y5, D16Y7, D16Y8, and B16A2; a 16-pin Data Link Connector (DLC) provides OBD2 scan-tool access. The ECM/PCM mounts behind the passenger-side kick panel.
Connector A
| Pin | name | Signal |
|---|---|---|
| A8 | VTEC Solenoid Valve | Analog |
| A10 | Power Ground | Ground |
| A20 | Ignition Control Module | RPM |
| A23 | Power Ground | Ground |
Connector C
| Pin | name | Signal |
|---|---|---|
| C15 | VTEC Pressure Switch | Analog |
| C18 | Vehicle Speed Sensor | Speed |
Connector D
| Pin | name | Signal |
|---|---|---|
| D1 | Throttle Position Sensor | Analog |
| D2 | Engine Coolant Temperature Sensor | Analog |
| D3 | MAP Sensor | Analog 0.32V @ -13.9 PSI 4.84V @ 10.94 PSI |
| D5 | Brake Switch | Analog |
| D7 | Primary O2 Sensor | Analog |
| D8 | Intake Air Temperature Sensor | Analog |
| D14 | Secondary O2 Sensor | Analog |
Notes
The ECM/PCM uses multiple connectors; this page documents the selected signal pins relevant to VTEC, ignition, and sensor inputs. On VTEC-equipped models (D16Y8, B16A2), connector A pin A8 drives the VTEC solenoid valve output, while connector C pin C15 carries the VTEC oil pressure switch signal back to the ECM. The pin numbering orientation follows Honda convention: connectors are read from the wire side (harness side) with the locking tab at the top. Pins A10 and A23 are power ground references. The OBD2 16-pin DLC provides access for Honda PGM Tester and generic scan tools per SAE J1962. To clear stored diagnostic trouble codes (DTCs), disconnect the negative battery terminal for at least 30 seconds, or remove the ECM backup fuse; this also clears idle learn data, which requires an idle relearn procedure afterwards.
Signals
- VTEC Solenoid Valve (A8) — ECM output that energises the VTEC solenoid to switch cam profiles on VTEC engines; present on D16Y8 and B16A2 variants
- Power Ground (A10, A23) — chassis/power ground references for the ECM
- Ignition Control Module (A20) — RPM signal exchanged between the ECM and the ignition control module for timing control
- VTEC Pressure Switch (C15) — input from the VTEC oil pressure switch, confirming oil pressure is sufficient before VTEC engages; used on 1996–1998 models (connector designation changes to C101 for 1999–2000)
- Vehicle Speed Sensor (C18) — vehicle speed pulse signal to the ECM, used for fuel cut, idle control, and speed-dependent corrections
- Throttle Position Sensor (D1) — analogue voltage representing throttle plate angle
- Engine Coolant Temperature Sensor (D2) — analogue voltage from the ECT sensor; used for fuel enrichment, ignition timing, and fan control
- MAP Sensor (D3) — manifold absolute pressure; analogue output ranging approximately 0.32 V at −13.9 PSI to 4.84 V at 10.94 PSI; primary load signal for PGM-FI fuel calculation
- Brake Switch (D5) — signal from the brake pedal switch; used by the ECM for torque converter lock-up control (automatic transmission) and idle-up logic
- Primary O2 Sensor (D7) — upstream (pre-catalyst) heated oxygen sensor signal; primary closed-loop fuel trim input
- Intake Air Temperature Sensor (D8) — analogue voltage from the IAT sensor in the air intake path; used to correct fuel delivery for air density
- Secondary O2 Sensor (D14) — downstream (post-catalyst) oxygen sensor signal; used for catalyst efficiency monitoring under OBD2