Description & Operation: Notes

The Electronic Control Unit (ECU) receives signals from various sensors, consults appropriate memory and sends output signals to various control devices. This provides an extremely accurate control of air/fuel mixture and idle speed under all operating conditions.

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

The ECU also controls cold start system, electric fuel pump and fuel cut-off systems. The ECU also contains a fail-safe system to monitor sensors and detect any abnormality in ECU. This provides safe driving even if 1 or more of the sensors are faulty or the ECU malfunctions.

There are 10 sensors used to provide operating information to the ECU in this system. These are: Crank angle sensors (TDC and CYL), manifold absolute pressure sensor (MAP), atmospheric pressure sensor, coolant temperature sensor, intake air temperature sensor, throttle angle sensor, oxygen sensor (O2), idle mixture adjuster sensor and starter switch.

The electronic control system has a self-diagnostic function to help find and fix any 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 below driver's seat.