The 1993–1994 Nissan Altima uses the KA24DE 2.4 litre DOHC inline-four engine managed by Nissan’s ECCS (Electronic Concentrated Control System), which provides sequential multi-point fuel injection and electronic ignition timing from a single ECM. The ECM connector is a multi-pin proprietary Nissan unit sharing the same family architecture used across the US-market Nissan range of that era, including the contemporary S13 240SX. These model years predate the mandatory OBD-II standard; the Altima uses OBD-I diagnostics accessible via a self-diagnostic mode.
ECU - Electronic Control Unit Connector.
| Pin | name | Signal |
|---|---|---|
| 2 | Tachometer Signal | RPM |
| 16 | Mass Air Flow Sensor | Analog |
| 17 | Mass Air Flow Sensor Ground | Ground |
| 18 | Engine Coolant Temperature Sensor | Analog |
| 19 | O2 Sensor Signal | Analog |
| 20 | Throttle Position Sensor | Analog |
| 21 | Sensor Ground | Ground |
| 26 | Air Temperature Sensor | Analog |
| 32 | Vehicle Speed Sensor | Speed |
| 48 | Power Ground (Electronic Concentrated Control System) | Ground |
| 101 | Injector # 1 | Speed |
| 103 | Injector # 3 | Speed |
| 110 | Injector # 2 | Speed |
| 112 | Injector # 4 | Speed |
| 116 | Power Ground (Electronic Concentrated Control System) | Ground |
Notes
The connector is a proprietary Nissan multi-pin ECM header. Only the pins documented in factory wiring diagrams are listed; remaining positions are either unused or not publicly documented. Diagnostics are OBD-I; fault codes are retrieved via the self-diagnostic mode on the ECM, not a standardised OBD-II DLC.
Signals
- Tachometer Signal — engine speed output from the ECM to the instrument cluster tachometer, in RPM.
- Mass Air Flow Sensor — analogue voltage signal from the hot-wire MAF sensor indicating intake air mass flow rate.
- Mass Air Flow Sensor Ground — dedicated signal ground for the MAF sensor circuit.
- Engine Coolant Temperature Sensor — analogue voltage input from the coolant temperature thermistor; used for fuel enrichment and ignition timing correction.
- O2 Sensor Signal — analogue voltage from the exhaust oxygen (lambda) sensor; used by the ECM for closed-loop fuelling correction.
- Throttle Position Sensor — analogue voltage input indicating throttle plate angle.
- Sensor Ground — common signal ground for sensor reference circuits.
- Air Temperature Sensor — analogue voltage input from the intake air temperature sensor; used for air-density compensation.
- Vehicle Speed Sensor — pulse signal from the vehicle speed sensor; used for speed-dependent fuel and ignition corrections.
- Power Ground (Electronic Concentrated Control System) — chassis power ground for the ECCS control unit (pins 48 and 116).
- Injector #1, #2, #3, #4 — individual injector drive signals for each cylinder; the ECM switches each injector to ground to trigger sequential fuel injection.