The 1999 Infiniti G20 (P11 chassis) uses Nissan’s ECCS (Electronic Concentrated Control System) engine management. The Engine Control Module (ECM) drives the SR20DE 2.0-litre inline-four with port fuel injection and is OBD-II compliant, featuring dual oxygen sensors for closed-loop fuelling on both catalyst banks. The P11 ECM harness connector layout differs from the earlier P10 generation; notably, the intake air temperature sensor moved to pin 28 and auxiliary power was removed from pin 70. The ECM monitors mass airflow, coolant temperature, throttle position, vehicle speed, and both oxygen sensors to calculate injector pulse width and ignition timing.
ECU - Electronic Control Unit Connector.
| Pin | name | Signal |
|---|---|---|
| 3 | Tachometer Signal | RPM |
| 23 | Throttle Position Sensor | Analog |
| 26 | Vehicle Speed Sensor | Speed |
| 28 | Intake Air Temperature Sensor | 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 |
| 102 | Injector # 1 | Speed |
| 104 | Injector # 3 | Speed |
| 107 | Injector # 2 | Speed |
| 109 | Injector # 4 | Speed |
| 118 | Power Ground (Electronic Concentrated Control System) | Ground |
Notes
The ECM harness connector uses a lever-release multi-pin plug. Disconnect the negative battery terminal before unplugging the ECM. The P11 connector layout is not interchangeable with the P10 (1991–1993) connector.
Signals
- Tachometer Signal (pin 3) — engine speed (RPM) output to instrument cluster
- Throttle Position Sensor (pin 23) — analogue 0–5 V signal indicating throttle plate angle
- Vehicle Speed Sensor (pin 26) — pulse signal from transmission for speed-dependent fuelling corrections
- Intake Air Temperature Sensor (pin 28) — analogue NTC input; pin position changed from pin 26 on P10 to pin 28 on P11
- O2 Sensor Signal Front (pin 46) — upstream (pre-catalyst) oxygen sensor; primary closed-loop lambda input
- Mass Air Flow Sensor (pin 47) — analogue voltage from hot-wire MAF sensor
- Mass Air Flow Sensor Ground (pin 48) — dedicated signal ground for MAF sensor
- Sensor Ground (pin 50) — common analogue sensor reference ground
- Engine Coolant Temperature Sensor (pin 51) — analogue NTC input for coolant temperature
- O2 Sensor Signal Rear (pin 52) — downstream (post-catalyst) oxygen sensor; OBD-II catalyst monitor
- Injector #1 (pin 102) — fuel injector driver, cylinder 1
- Injector #3 (pin 104) — fuel injector driver, cylinder 3
- Injector #2 (pin 107) — fuel injector driver, cylinder 2
- Injector #4 (pin 109) — fuel injector driver, cylinder 4
- Power Ground ECCS (pin 118) — main ECM power ground for ECCS system