System Outline

The engine control system utilizes a microcomputer to maintain overall control of the engine, transmission, etc. an outline of engine control is given here.

1. INPUT SIGNALS
1. Engine Coolant Temp. (Water Temp.) Signal System
The engine coolant temp. sensor (EFI water temp. sensor) detects the engine coolant temp. And has a built-in thermistor with a resistance which varies according to the engine coolant temp. (water temp.) Thus the engine coolant temp. (water temp.) is input in the form of a control signal to TERMINAL THW of the engine control module (ECU)
2. Intake Air Temp.signal System
The intake air temp. sensor is installed in the mass air flow (air flow meter) and detects the intake air temp., which is input as a control signal to TERMINAL THA of the engine control module (ECU)
3. Oxygen Sensor Signal System
The oxygen density in the exhaust emissions is detected and input as a control signal to TERMINALS OX1 and OX2 of the engine control module (ECU).
4. RPM Signal System
Crankshaft position and engine rpm are detected by the pickup coil installed inside the distributor. Crankshaft position is input as a control signal to TERMINAL G1 or G2 of the engine control module (ECU), and rpm is input to TERMINAL NE.
5. Throttle Signal System
The throttle position sensor detects the throttle valve opening angle, which is input as a control signal to TERMINAL VTA of the engine control module (ECU), or when the valve is fully closed, to TERMINAL IDL.
6. Vehicle Speed Signal System
The vehicle speed is detected by the vehicle speed sensor installed inside the combination meter, detects the vehicle speed and inputs a control signal to TERMINAL SP1 of the engine control module (ECU).
7. Park/Neutral Position SW (neutral Start SW) Signal System
The park/neutral position SW (neutral start SW) detects whether the shift position is in neutral or not, and inputs a control signal to TERMINAL NSW of the engine control module (ECU)
8. A/C SW Signal System
The operating voltage of the A/C magnetic clutch is detected and input in the form of a control signal to TERMINAL A/C of the engine control module (ECU).
9. Battery Signal System
Voltage is constantly applied to TERMINAL BATT of the engine control module (ECU). When the ignition SW is turned to ON, voltage for engine control module (ECU) operation is applied via the MFI main relay (EFI main relay) to TERMINAL +B of the engine control module (ECU).
10. Intake Air Volume Signal System
Intake air volume is detected by the potentiometer installed inside the volume air flow (air flow meter) and is input as a control signal to TERMINAL VS of the engine control module (ECU).
11. STA Signal System
To confirm that the engine is cranking, the voltage applied to the starter motor during cranking is detected and is input as a control signal to TERMINAL STA of the engine control module (ECU)
12. Engine Knock Signal System
Engine knocking is detected by the knock sensor and input as a control signal to TERMINAL KNK of the engine control module (ECU).

2. CONTROL SYSTEM
^ MFI Multiport Fuel Injection (EFI)) System
The MFI (EFI ( system monitors the engine revolutions through the signals each sensor (input signals (1) to (11)) inputs to the engine control module (ECU) based ON this data and the program memorized in the engine control module (ECU), the most appropriate time of fuel injection is decided and current is output to TERMINALS #10 and #20 of the engine control module (ECU), causing the injectors to operate it (to inject fuel) . It is this system which, through the work of the engine control module (ECU), finely controls fuel injection in response to driving conditions.
^ ESA (Electronic Spark Advance) System
The ESA system monitors the engine revolutions using the signals (input signals (1, 4, 5, 6, 10, 11, 13)) input to the engine control module (ECU) from each sensor. Based ON this data and the program memorized in the engine control module (ECU), the most appropriate ignition timing is decided and current is output to TERMINAL IGT of the engine control module (ECU) . This output controls the igniter to produce the most appropriate ignition timing for the driving conditions.
^ IAC (Idle Air Control (ISC)) System
The IAC (ISC) system (rotary solenoid type) increases the rpm and provides idling stability for fast idle-up when the engine is cold and when the idle speed has dropped due to electrical load, etc, the engine control module (ECU) evaluates the signals from each sensor (input signals (1, 2, 4 to 8, 11)), outputs current to TERMINALS ISCC and ISCO, and controls the idle air control valve (ISC valve)
^ A/C Cut Control System
When the throttle valve angle exceeds a predetermined valve, the A/C is turned OFF for a specified period of time to improve acceleration performance.
The engine control module (ECU) receives input signals (5), and outputs signals to TERMINAL ACT.
^ Fuel Pressure Control System
The fuel pressure up system causes the VSV (for fuel pressure up) to come ON for high temp. Starts and for about 120 Seconds after starting in order to increase the fuel pressure, improve startability at high temperatures and provide stable idling the engine control module (ECU) evaluates the input signals from each sensor (1 and 11) outputs current to TERMINAL FPU and controls the VSV.
^ Oxygen Sensor Heater Control System
The oxygen heater control system turns the heater to ON when the intake air volume is low (temp. of exhaust emission low), and warms up the heated oxygen sensor (oxygen sensor) to improve detection performance of the sensor, the engine control module (ECU) evaluates the signals from each sensor (input signals (1, 9, 10, 11)), current is output to TERMINALS HT or HT2 and controls the heater.

3. DIAGNOSIS SYSTEM
With the diagnosis system, when there is a malfunctioning in the engine control module (ECU) signal system, the malfunction system is recorded in the memory. The malfunctioning system can then be found by reading the display (code) of the malfunction indicator lamp (check engine warning light)

4. FAIL-SAFE SYSTEM
When a malfunction occurs in any system, if there is a possibility of engine trouble being caused by continued control based ON the signals from that system, the fail-safe system either controls the system by using data (standard values) recorded in the engine control module (ECU) memory or else stops the engine