Computers and Control Systems: Description and Operation

This system utilizes an engine control module and maintains overall control of the engine, transmission and so on. An outline of the engine control is explained here.

1. INPUT SIGNALS
1. Engine coolant temp. signal circuit
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. thus the engine coolant temp. is input in the form of a control signal into TERMINAL THW of the engine control module.
2. Intake air temp. signal circuit
The intake air temp. sensor detects the intake air temp., which is input as a control signal into TERMINAL THA of the engine control module.
3. Oxygen sensor signal circuit
The oxygen density in the exhaust gases is detected and input as a control signal into TERMINAL OX1 (except California) and OX2 of the engine control module.
4. RPM signal Circuit
Camshaft position and crankshaft position are detected by the camshaft position sensor and crankshaft position sensor. Camshaft position is input as a control signal into TERMINAL G+, of the engine control module, and engine RPM is input into TERMINAL NE+.
5. Throttle signal Circuit
The throttle position sensor detects the throttle valve opening angle, which is input as a control signal into TERMINAL VTA of the engine control module.
6. Vehicle speed signal circuit
The vehicle speed sensor, installed inside the transmission, detects the vehicle speed and inputs a control signal into TERMINAL SPD of the engine control module.
7. Park/Neutral position SW signal circuit (A/T)
The Park/Neutral position SW detects whether the shift position are in neutral, parking or not, and inputs a control signal into TERMINAL STA of the engine control module.
8. A/C SW signal circuit
The A/C amplifier function is built in the engine control module. The A/C SW signal inputs into the TERMINAL A/C SW of the engine control module.
9. Battery signal circuit
Voltage is constantly applied to TERMINAL BATT of the engine control module. When the ignition SW is turned ON, the voltage for engine control module start-up power supply is applied to TERMINAL +B of engine control module via EFI main relay.
10. Intake air volume signal circuit
Intake air volume is detected by the manifold absolute pressure sensor (for manifold pressure) and is input as a control signal into TERMINAL PIN of the engine control module.
11. Starter signal circuit
To confirm whether the engine is cranking, the voltage applied to the starter motor during cranking is detected and the signal is input into TERMINAL NSW of the engine control module as a control signal.
12. Engine knock signal circuit
Engine knocking is detected by knock sensor 1 and the signal is input into TERMINAL KNK as a control signal.
13. Electrical load signal circuit
The signal when systems such as the rear window defogger, headlights, etc. which cause a high electrical burden are ON is input to TERMINAL ELS as a control signal.
14. Air fuel ratio signal circuit (California)
The air fuel ratio is detected and input as a control signal into TERMINAL AF+ of the engine control module.

2. CONTROL SYSTEM
- SFI (Sequential multiport Fuel Injection) System
The SFI system monitors the engine condition through the signals, which are input from each sensor (input signals from (1) to (14) etc.) to the engine control module. The best fuel injection volume is decided based on this data and the program memorized by the engine control module, and the control signal is output to TERMINALS #10, #20, #30 and #40 of the engine control module to operate the injector. (inject the fuel). The SFI system produces control of fuel injection operation by the engine control module in response to the driving conditions.
- ESA (Electronic Spark Advance) System
The ESA system monitors the engine condition through the signals, which are input to the engine control module from each sensor (input signals from (1), (2), (4) to (12) etc.) the best ignition timing is detected according to this data and the memorized data in the engine control module, and the control signal is output to TERMINALS IGT1 and IGT2. This signal controls the igniter to provide the best ignition timing for the driving conditions.
- Idle Air Control System (IAC)
The IAC system (step motor 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 evaluates the signals from each sensor (input signals (1), (4) to (8), (13) etc.), outputs current to TERMINALS ISCO and ISCC, and controls the idle air control valve.
- Fuel pump control system
The engine control module operation outputs to TERMINAL FCand controls the CIR OPN relay. Thus controls the fuel pump drive speed in response to conditions.
- EGR control system
The EGR cut control system controls the [1][2][3][4]VSV (EGR) by evaluating the signals from each sensor which are input to the engine control module (input signals (1), (5), (6), (9) etc.) and by sending output to TERMINAL EGR of the engine control module.
- A/C conditioning operation system
In addition to the conventional A/C cut control, the engine control module performs the air conditioning operation as well since the A/C amplifier function is built in it.

3. DIAGNOSIS SYSTEM
With the diagnosis system, when there is a malfunctioning in the engine control module 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.

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 memory or else stops the engine.