Computers and Control Systems: Description and Operation
The engine control system utilize a microcomputer and maintains overall control of the engine, transmission, etc. An outline of engine control is given here.1. INPUT SIGNAL
1. Engine coolant temp. signal system
The engine coolant temp. sensor detects the engine coolant temp. and has a built-in thermistor with a resistance which varies according to the engine coolant temp. The engine coolant temp. is input as a control signal to TERMINAL THW of the engine control module.
2. Heated oxygen sensor signal system
The oxygen density in the exhaust emissions is detected and input as a control signal to TERMINAL OX1 or OX2 of the engine control module. To maintain stable detection performance by the heated oxygen sensor, the heated oxygen sensors are warmed. The heater is also controlled by the engine control module (HT1 or HT2).
3. RPM signal system
Camshaft position and crankshaft position are detected by the camshaft position sensor and crankshaft position sensor, camshaft position is input as a control signal to TERMINAL G+ of the engine control module, and engine RPM is input to TERMINAL NE+.
4. 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.
5. Vehicle speed signal system
The vehicle speed sensor, detects the vehicle speed and input to ABS speed sensor of the ABS ECU, from ABS ECU to TERMINAL SP1 ot the engine control module.
6. A/C SW signal system
The operating voltage of the A/C magnetic clutch is detected and input as a control signal to TERMINAL AC1 of the engine control module.
7. Battery signal system
Voltage is constantly applied to TERMINAL BATT of the engine control module. When the ignition SW is turned to ON, voltage for engine control module operation is applied via the EFI relay to TERMINAL +B of the engine control module.
8. Intake air volume signal system
Intake air volume is detected by the mass air flow meter and a signal is input into TERMINAL VG of the engine control module as a control signal.
9. Stop light SW signal system
The stop light SW is used to detect whether or not the vehicle is braking and the information is input as a control signal to TERMINAL BK of the engine control module.
10. Starter 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.
11. Engine knock signal system
Engine knocking is detected by the knock sensor no. 1 and no. 2 and the signals are input to TERMINALS KNK1 and KNK2 of the engine control module.
12. 4WD signal system (4WD)
Whether or not the vehicle is operating in 4WD module is determined, and a control signal is input to TERMINAL 4WD of the engine control module.
13. Intake air temp. signal circuit
The intake air temp. sensor is installed in the mass air flow meter and detects the intake air temp., which is input as a control signal into TERMINAL THA of the engine control module.
2. CONTROL SYSTEM
* SFI system
The SFI system monitors the engine conditions through the signals each sensor (Input signals (1 to 13)) inputs to the engine control module. Based on this data and the program memorized in the engine control module, the most appropriate fuel injection timing is detected and current is output to TERMINALS #10, #20, #30, #40 ,#50and #60 of the engine control module, causing the injectors to operate (to inject fuel). It is this system which, through the work of the engine control module, finely controls fuel injection in response to driving conditions.
* ESA system
The ESA system monitors the engine conditions using the signals (Input signals (1, 3, 4 to 6, 8, 10,11)) input to the engine control module from each sensor. Based on this data and the program memorizes in the engine control module, the most appropriate ignition timing is decided and current is output to TERMINALS IGT1, IGT2and IGT3 of the engine control module. This output controls the igniter to produce the most appropriate ignition timing for the driving conditions.
* Heated oxygen sensor heater control system
The heated oxygen sensor heater control system turns the heater to ON when the intake air volume is low Temp. of exhaust emissions is low). And warms up the heated oxygen sensors to improve detection performance of the sensors. The engine control module evaluates the signals from each sensor (Input signals (1, 3, 7, 8, 10)) current is output to TERMINAL HT1 or HT2 and controls the heater.
3. DIAGNOSIS SYSTEM
With the diagnosis system, when there is a malfunction in the ECU signal system, the malfunctioning system is recorded in the memory. The malfunctioning system can then be found by reading the display (Code) of the malfunction indicator lamp.
4. FAIL- SAFE SYSTEM
When a malfunction occurs in any system, if there is a possibility of engine 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 memory or else stops the engine.