EFI SYSTEM — System Description FI-3 By means of the ECU, the TCCS controls the fol- lowing functions: 1. Electronic Fuel Injection (EFI) The ECU receives signals from various sensors indicating changing engine operating condi- tions such as: Intake air volume Engine air temperature Coolant temperature Engine rpm Acceleration/deceleration Exhaust oxygen content etc. These signals are utilized by the ECU to de- termine the injection duration necessary for an optimum air fuel ratio. 2 Electronic Spark Advance (ESA) The ECU is programmed with data for opti- mum ignition timing under any and all operat- ing conditions. Using data provided by sensors which monitor various engine functions (rpm, intake air volume, coolant temperature, etc.), the microcomputer (ECU) triggers the spark at precisely the right instant. (See IG section) 3. Idle Speed Control (ISC) The ECU is programmed with target engine speed values to respond to different engine conditions (coolant temperature, air condition- er on/off, etc.). Sensors transmit signals to the ECU which controls the flow of air through the by-pass of the throttle valve and adjusts idle speed to the target value. (See pages FI-43,60) 4. Exhaust Gas Recirculation (EGR) The ECU detects the coolant temp. and con- trols EGR function accordingly. (See page EC-10) 5. Electronically Controlled Transmission (ECT) (Automatic Trans. only) A serial signal is transmitted to the ECT com- puter to prevent shift up to 3rd or overdrive during cold engine operation. (See AT section) 6. Diagnostics The ECU detects any malfunctions or abnor- malities in the sensor network and lights a "CHECK ENGINE" warning light on the instru- ment panel. At the same time, the trouble is identified and a diagnostic code is recorded by the ECU. The diagnostic code can be read by the number of blinks of the "CHECK ENGINE" warning light when check connector are short- circuited. (See page FI-22) 7. Fail-Safe Function In the event of a computer malfunction, a back-up circuit will take over to provide minimal drivability. Simultaneously, the "CHECK ENGINE" warning light is activated.