Description & Operation: Notes

The ECU is the main controlling device of the electronic control system. The Electronic Control Unit (ECU) receives signals from various sensors. ECU uses these signals to determine outputs to various control devices. ECU is mounted below passenger seat.

The ECU contains memories for the basic injector durations at various engine RPM and Manifold Absolute Pressures (MAP). The basic injector duration is read from calibration tables built into ECU internal memory. The ECU modifies the basic injector duration according to input signals from various sensors to obtain the final injector duration. The ECU on Acura models also controls ignition timing advance curve based upon sensor input signals.

The ECU also controls cold start system, electric fuel pump and fuel cut-off systems. The ECU contains a fail-safe system which monitors input signals, substituting pre-calibrated values in the event it detects any abnormalities. This provides safe driving (limp-home mode) even if one or more of the sensors are faulty, or the ECU malfunctions.

There are several input devices which provide operating information to the ECU. These include the throttle position sensor, crank angle sensor(s), vehicle speed sensor (in dash), Manifold Absolute Pressure (MAP) sensor, Atmospheric Pressure (PA) sensor, Coolant Temperature (TW) sensor, Intake Air Temperature (TA) sensor, oxygen sensor, Idle Mixture Adjuster (IMA) sensor, starter crank signal and electronic load detector.

NOTE: Crank angle sensor input signals vary depending on vehicle application.

The ECU has a self-diagnostic capability. This system uses a dash-mounted PGM-FI or Check Engine warning light and one or 2 ECU mounted self-diagnostic lights. All models use a Red LED on ECU for display of system failure codes. As a bulb check, the PGM-FI or Check Engine warning light on instrument panel will glow for 2-8 seconds when ignition switch is turned to the "ON" position.