Description & Operation: Notes

The Electronic Control Unit (ECU) receives signals (data) from various sensors. The ECU processes input data and sends output signals to various control devices. This allows for precise control of air/fuel mixture and idle speed under all operating conditions.

The ECU is the main controlling device of the electronic control system. The ECU contains memories for basic injector pulses at various engine speeds (RPM) and manifold absolute pressures (air volume). The basic injector pulse is read out of the memory of ECU. The ECU modifies basic injector pulse according to input signals from various sensors. This allows the ECU to obtain optimum injector pulse.

The ECU also controls cold start system, electric fuel pump and fuel cut-off systems. The ECU contains a fail-safe system to monitor sensors and detect any abnormality in ECU itself. This provides safe driving even if one or more of the sensors are faulty or ECU malfunctions.

There are 10 sensors used to provide operating information to the ECU in this system. The 10 sensors are: Crank angle sensors (TDC and CYL), manifold absolute pressure sensor, atmospheric pressure sensor, coolant temperature sensor, intake air temperature sensor, throttle angle sensor, oxygen sensor, idle mixture adjuster sensor and starter switch.

The electronic control system has a self-diagnostic function to help locate and correct problems. This system uses a dash mounted PGM-FI warning light and 4 ECM mounted self-diagnostic lights. The PGM-FI warning light will glow for 2 seconds when ignition switch is turned on. The ECU is mounted below passenger seat (Civic CRX Si), or on driver's center pillar, next to seat (Prelude).