The ECU - Electronic Control Unit is an embedded system that controls one or more of the electrical systems or subsystems in a vehicle.
ECU - Electronic Control Unit Connector.
Early-production 1995 Nissan 240SX models used the S14 chassis with a KA24DE 2.4-litre DOHC inline-four engine managed by Nissan’s ECCS (Electronic Concentrated Control System). The ECM provides sequential multi-point fuel injection and electronic ignition timing control through a 76-pin connector, and communicates with diagnostics equipment via the OBD-I self-diagnostic mode. Later 1995 production switched to OBD-II; this page covers the early OBD-I variant only.
| Pin | name | Signal |
|---|---|---|
| 3 | Tachometer Signal | RPM |
| 23 | Throttle Position Sensor | Analog |
| 26 | Vehicle Speed Sensor | Speed |
| 33 | Throttle Position Sensor (A/T) | Analog |
| 46 | O2 Sensor Signal (Front) | Analog |
| 47 | Mass Air Flow Sensor | Analog |
| 48 | Mass Air Flow Sensor Ground | Ground |
| 50 | Sensor Ground | Ground |
| 51 | Engine Coolant Temperature Sensor | Analog |
| 52 | O2 Sensor Signal (Rear) | Analog |
| 63 | Intake Air Temperature Sensor | Analog |
| 70 | Power Supply (Aux) | Power |
| 102 | Injector # 1 | Speed |
| 104 | Injector # 3 | Speed |
| 107 | Injector # 2 | Speed |
| 109 | Injector # 4 | Speed |
| 112 | Power Ground (Electronic Concentrated Control System) | Ground |
| 118 | Power Ground (Electronic Concentrated Control System) | Ground |
Notes
This page covers only the OBD-I ECM fitted to early 1995 240SX (S14) production. The 1995 model year was transitional; later builds carried an OBD-II ECM with a revised connector layout. The table lists selected signal pins; unlisted positions are unassigned or carry internal ECCS functions not exposed in publicly available documentation.
Signals
- Tachometer Signal — engine speed pulse output from the ECM to the instrument cluster tachometer.
- Throttle Position Sensor — analogue voltage from the TPS indicating throttle plate angle; used for fuel and ignition calculations.
- Throttle Position Sensor (A/T) — second TPS input used by the ECM on automatic transmission-equipped vehicles.
- Vehicle Speed Sensor — pulse signal from the transmission indicating road speed; used for idle-up and fuel cut strategies.
- O2 Sensor Signal (Front) — analogue voltage from the upstream heated oxygen sensor; used for closed-loop fuel trim.
- O2 Sensor Signal (Rear) — analogue voltage from the downstream oxygen sensor; used for catalyst monitoring.
- Mass Air Flow Sensor — analogue voltage from the hot-wire MAF sensor indicating inducted air mass.
- Mass Air Flow Sensor Ground — dedicated signal ground for the MAF sensor.
- Sensor Ground — common reference ground for analogue sensor inputs.
- Engine Coolant Temperature Sensor — analogue voltage from the ECT sensor; used for warm-up enrichment and fan control.
- Intake Air Temperature Sensor — analogue voltage from the IAT sensor; used for charge-density compensation.
- Power Supply (Aux) — auxiliary battery-backed power supply to retain ECM memory during ignition-off.
- Injector #1 / #2 / #3 / #4 — individual sequential injector drive signals; the ECM switches each low-side driver in firing-order sequence.
- Power Ground (ECCS) — high-current chassis ground returns for the ECM power stage; two separate ground pins reduce impedance on the power circuit.