System Outline
The engine control system utilizes a microcomputer and maintains overall control of the engine, transmission etc. An outline of the engine control is given 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. which is input into TERMINAL THW of the engine control module as a control signal.
(2) 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 to TERMINAL THA of the engine control module.
(3) Oxygen density signal circuit
The oxygen density in the exhaust emission is detected by the heated oxygen sensors side and input as a control signal to TERMINALS OX1, OX2, OXR1 and OXR2 of the engine control module.
(4) RPM signal circuit
Camshaft position is detected by the camshaft position sensor No. 1 and No. 2 and its signal is input to TERMINALS G2 of the engine control module as a control signal.
Also, engine RPM is detected by the crankshaft position sensor and input as a control signal to TERMINAL NE.
(5) Throttle position signal circuit
The throttle position sensor detects the throttle valve opening angle as a control signal, which is input into TERMINAL VPA 1 of the engine control module.
The throttle position sensor detects the throttle valve opening angle as a control signal, which is input into TERMINAL VTA of the engine control module.
(6) Vehicle speed circuit
The vehicle speed is detected by vehicle speed sensor No. 1 installed in the transmission and the signal is input to TERMINAL SP2+ of the engine control module.
(7) Neutral position signal circuit
The Park/Neutral position SW detects whether the shift position is in N and P or not, and the signal is input into TERMINAL NSW of the engine control module.
(8) A/C SW signal circuit
The operating voltage of the A/C magnetic clutch is detected and the signal is input into TERMINAL ACMG of the engine control module as a control signal.
(9) Battery signal circuit
Voltage is constantly applied to TERMINAL BATT of the engine control module. With the ignition SW turned ON, the voltage for engine control module start-up power supply is applied to TERMINAL +B of the engine control module via EFI main relay.
The current flowing through the IGN fuse flows to TERMINAL IGSW of the engine control module.
Voltage constantly applied to TERMINAL +BM of the engine control module
(10) Intake air volume signal circuit
Intake air volume is detected by the mass air flow meter and the signal is input to TERMINAL VG of the engine control module as a control signal.
(11) Stop light SW signal circuit
The stop light SW is used to detect whether the vehicle is braking or not and the signal is input into TERMINAL STP of the engine control module as a control signal.
(12) Start signal circuit
To confirm whether the engine is cranking, the voltage is applied to the starter motor during cranking is detected and the signal is input into TERMINAL STA of the engine control module as a control signal.
(13) Engine knock signal circuit
Engine knocking is detected by knock sensors (front and rear side) and the signal is input into TERMINALS KNK1 and KNK2 as a control signal.
2. CONTROL SYSTEM
* SFI system
The SFI system monitors the engine condition through the signals input from each sensor (Input signals from (1) to (13) etc.) to the engine control module. The best fuel injection timing 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, #40, #50 and #60 of the engine control module to operate the injector (Inject the fuel). The SFI system produces controls of fuel injection operation by the engine control module in response to the driving conditions.
* ESA system
ESA system monitors the engine condition through the signals input to the engine control module from each sensor (Input signals from (1), (2), (4) to (13) etc.). The best ignition timing is decided according to this data and the memorized data in the engine control module and the control signal is output to TERMINALS IGT. This signals control the igniter to provide the best ignition timing for the driving conditions.
* Heated oxygen sensor heater control system
The main heated oxygen sensor sub heated oxygen sensor heater control system turns the heater ON when the intake air volume is low (Temp. of exhaust emissions is low), and warms up the oxygen sensors to improve detection performance of the sensors. The engine control module evaluates the signals from each sensor (Input signals from (1), (2), (4), (9) to (11) etc.), and outputs current to TERMINALS HTL, HTR, HTL2 and HTR2 to control the heater.
* Fuel pump control system
The engine control module outputs current to TERMINAL FPC and controls the fuel pump ECU and fuel pump drive speed in response to the driving conditions.
* ACIS
ACIS includes a valve in the bulkhead separating the surge tank into two parts. This valve is opened and closed in accordance with the driving conditions to control the intake manifold length in two stages for increased engine output in all ranges from low to high speeds.
3. DIAGNOSIS SYSTEM
With the diagnosis system, when there is a malfunction in the engine control module signal system the malfunctioning system is recorded in the memory. The malfunctioning system can be found by reading the code displayed by the malfunction indicator lamp.
4. FAIL-SAFE SYSTEM
When a malfunction has occurred 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.