ECU - Electronic Control Unit Connector.
The 1998–2002 Honda Accord (6th generation, CG1/CG2/CG5/CG6 chassis) uses an OBD2-compliant Engine Control Module (ECM/PCM) as part of Honda’s PGM-FI (Programmed Fuel Injection) system. The ECM manages fuel injection, ignition timing, the VTEC solenoid valve (on VTEC-equipped engines), and the idle air control valve, while monitoring sensors including MAP, IAT, ECT, throttle position, and oxygen sensors. The module communicates with diagnostic equipment via a 16-pin Data Link Connector (DLC) in accordance with SAE J1962. Connectors are read from the wire side with the locking tab at the top.
Connector A
| Pin | name | Signal |
|---|---|---|
| A19 | Engine Speed Pulse | RPM |
| A23 | Secondary O2 Sensor | Analog |
| A32 | Brake Switch | Analog |
Connector B
| Pin | name | Signal |
|---|---|---|
| B10 | Power Ground | Ground |
| B12 | VTEC Solenoid Valve | Analog |
Connector C
| Pin | name | Signal |
|---|---|---|
| C10 | VTEC Pressure Switch | Analog |
| C16 | Primary O2 Sensor | Analog |
| C17 | MAP Sensor | Analog 0.32V @ -13.9 PSI 4.84V @ 10.94 PSI |
| C23 | Vehicle Speed Sensor | Speed |
| C25 | Intake Air Temperature Sensor | Analog |
| C26 | Engine Coolant Temperature Sensor | Analog |
| C27 | Throttle Position Sensor | Analog |
Notes
The ECM is located in the passenger compartment. Connector pins are numbered and read from the wire side (rear of connector) with the locking tab oriented upward. The VTEC solenoid valve output (B12) and VTEC oil pressure switch input (C10) are present only on VTEC-equipped engine variants (F23A1 VTEC; V6 models use a separate PCM arrangement). To clear stored DTCs, disconnect the negative battery terminal for at least 30 seconds or remove the ECM backup fuse; note that idle learn data is also cleared and an idle relearn procedure is required afterwards.
Signals
- A19 Engine Speed Pulse — RPM signal output from the ECM, used by ancillary systems such as the instrument cluster tachometer.
- A23 Secondary O2 Sensor — Downstream (post-catalyst) heated oxygen sensor signal; ECM uses this to monitor catalytic converter efficiency.
- A32 Brake Switch — Input from the brake pedal position switch; ECM uses this signal for fuel cut and torque converter lock-up logic.
- B10 Power Ground — Main ECM power ground return; chassis ground reference for ECM power supply circuits.
- B12 VTEC Solenoid Valve — ECM-controlled output that energises the VTEC oil pressure solenoid to switch the valve timing profile on VTEC engines.
- C10 VTEC Pressure Switch — Input from the VTEC oil pressure switch confirming that hydraulic pressure has risen sufficiently for VTEC engagement.
- C16 Primary O2 Sensor — Upstream (pre-catalyst) heated oxygen sensor signal; primary input for closed-loop fuel trim.
- C17 MAP Sensor — Manifold Absolute Pressure sensor signal (0.32 V at −13.9 PSI vacuum; 4.84 V at 10.94 PSI boost); primary engine load input for fuel and ignition calculations.
- C23 Vehicle Speed Sensor — Vehicle speed pulse signal input; used for speed-dependent fuel cut, idle control, and instrument cluster.
- C25 Intake Air Temperature Sensor — IAT sensor signal; ECM uses inlet air temperature to correct fuel delivery and ignition timing.
- C26 Engine Coolant Temperature Sensor — ECT sensor signal; used for cold-start enrichment, cooling fan control, and temperature gauge output.
- C27 Throttle Position Sensor — TP sensor signal; indicates throttle plate angle for transient fuel enrichment and idle detection.