The Honda S2000 (AP1, 2000–2003; AP2, 2004–2005) uses an OBD2-compliant Engine Control Module (ECM) located under the driver’s seat. The ECM manages the PGM-FI (Programmed Fuel Injection) system for the high-revving F20C1 2.0-litre DOHC VTEC engine (AP1) and the F22C1 2.2-litre unit fitted to AP2 models. Three multi-pin connectors are used: Connector A (32-pin), Connector B (25-pin), and Connector C (31-pin). From the 2001 model year onward, Honda adopted SAE J1930 terminology for sensor designations such as ECT, IAT, MAP, TP, and HO2S.
ECU - Electronic Control Unit Connector.
Connector A
| Pin | name | Signal |
|---|---|---|
| A9 | Vehicle Speed Sensor | Speed |
| A19 | Engine Speed Pulse | RPM |
| A32 | Brake Switch | Analog |
Connector B
| Pin | name | Signal |
|---|---|---|
| B2 | Power Ground | Ground |
| B12 | VTEC Solenoid Valve | Analog |
Connector C
| Pin | name | Signal |
|---|---|---|
| C10 | VTEC Pressure Switch | Analog |
| C15 | Secondary O2 Sensor | Analog |
| C16 | Primary O2 Sensor | Analog |
| C17 | MAP Sensor | Analog 0.32V @ -13.9 PSI 4.84V @ 10.94 PSI |
| C25 | Intake Air Temperature Sensor | Analog |
| C26 | Engine Coolant Temperature Sensor | Analog |
| C27 | Throttle Position Sensor | Analog |
Notes
- The ECM is located under the driver’s seat; access requires seat removal.
- All connectors are read from the wire side (back of connector) with the locking tab at the top, which determines pin numbering orientation.
- A 16-pin Data Link Connector (DLC) per SAE J1962 is fitted for OBD2 scan tool and Honda PGM Tester access; it is separate from the ECM harness connectors.
- To clear stored Diagnostic Trouble Codes (DTCs), disconnect the negative battery terminal for at least 30 seconds or remove the ECM backup fuse; note that idle learn data is also erased and a relearn procedure is required afterwards.
- Connector A is a 32-pin housing; Connector B is a 25-pin housing; Connector C is a 31-pin housing. Only the pins listed here are documented; remaining positions vary by market and model year.
Signals
- Vehicle Speed Sensor (A9) — pulse signal from the vehicle speed sensor; used by the ECM to monitor road speed for fuel and idle control.
- Engine Speed Pulse (A19) — tachometer/RPM pulse output from the ECM; feeds the instrument cluster.
- Brake Switch (A32) — input from the brake pedal switch; signals the ECM when the brake is applied.
- Power Ground (B2) — main power ground reference for the ECM.
- VTEC Solenoid Valve (B12) — ECM output that energises the VTEC oil-pressure solenoid to engage the high-lift cam profile at the programmed engine speed threshold.
- VTEC Pressure Switch (C10) — input confirming hydraulic oil pressure has been established after VTEC engagement; monitored by the ECM to verify solenoid operation.
- Secondary O2 Sensor (C15) — downstream heated oxygen sensor (HO2S) signal used for catalyst efficiency monitoring under OBD2.
- Primary O2 Sensor (C16) — upstream heated oxygen sensor (HO2S) signal; primary feedback input for closed-loop fuel trim.
- MAP Sensor (C17) — Manifold Absolute Pressure sensor; analogue voltage input (approximately 0.32 V at −13.9 PSI to 4.84 V at +10.94 PSI) used to calculate engine load.
- Intake Air Temperature Sensor (C25) — IAT sensor input; used with MAP data to calculate air density for fuel delivery.
- Engine Coolant Temperature Sensor (C26) — ECT sensor input; used for cold-start enrichment, cooling fan control, and temperature-dependent fuel and ignition maps.
- Throttle Position Sensor (C27) — TP sensor analogue voltage input; indicates throttle opening angle for transient fuel corrections and idle detection.
References
- Honda S2000 2000–2003 Service Manual — Honda Motor Co.