ECU - Electronic Control Unit Connector.
The 1996–1997 Honda Accord (CD5/CD7/CD9 chassis) uses an OBD2-compliant Engine Control Module (ECM) as part of Honda’s PGM-FI (Programmed Fuel Injection) system. The transition from OBD1 to OBD2 brought a revised multi-connector ECM layout and a 16-pin Data Link Connector (DLC) for scan-tool access. The ECM manages fuel injection, ignition timing, idle air control, and — on VTEC-equipped variants — the solenoid valve controlling variable valve timing. It monitors inputs from the MAP, throttle position, engine coolant temperature, intake air temperature, and oxygen sensors.
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
Connectors are read from the wire side (back of connector) with the locking tab at the top; this orientation determines pin numbering. The ECM is located in the passenger-side kick panel area. An OBD2 16-pin DLC provides access for scan tools. To clear stored diagnostic trouble codes (DTCs), disconnect the negative battery terminal for 30 seconds or remove the ECM backup fuse; note that this also clears idle learn data, requiring an idle relearn procedure afterwards.
Signals
- VTEC Solenoid Valve (A8) — ECM output controlling the VTEC oil-pressure solenoid valve, which switches variable valve timing on VTEC-equipped engines
- Power Ground (A10, A23) — chassis/power ground reference for the ECM
- Ignition Control Module (A20) — RPM signal line between the ECM and the ignition control module
- VTEC Pressure Switch (C15) — input to the ECM from the oil-pressure switch confirming VTEC engagement
- Vehicle Speed Sensor (C18) — vehicle speed pulse signal input to the ECM
- Throttle Position Sensor (D1) — analogue voltage input reporting throttle plate angle
- Engine Coolant Temperature Sensor (D2) — analogue input for coolant temperature; used for fuel and ignition corrections
- MAP Sensor (D3) — manifold absolute pressure signal (0.32 V at −13.9 PSI; 4.84 V at 10.94 PSI); primary load input for fuel calculation
- Brake Switch (D5) — input indicating brake pedal application; used for idle and torque-converter lock-up control
- Primary O2 Sensor (D7) — upstream (pre-catalyst) heated oxygen sensor signal for closed-loop fuelling
- Intake Air Temperature Sensor (D8) — analogue input for incoming air temperature; used for fuel density corrections
- Secondary O2 Sensor (D14) — downstream (post-catalyst) oxygen sensor signal for catalyst efficiency monitoring