System Outline
The engine control system utilizes a microcomputer and maintains overall control of the engine, transmission etc. An outline of the engine control system is given here.
- Input Signals
- Engine coolant temp. signal circuit
The engine coolant temp. sensor detects the engine coolant temperature and has a built-in thermistor whose resistance varies according to the engine coolant temperature. The engine coolant temperature. is then input into TERMINAL THW of the engine control module as a control signal.
- Intake air temp. signal circuit
The intake air temp. sensor is installed in the mass air flow meter and detects the intake air temperature, which is input as a control signal to TERMINAL THA of the engine control module.
- Oxygen sensor signal circuit
The oxygen density in the exhaust emission is detected and is input as control signals from the heated oxygen sensors to TERMINALS OX1B and OX2B of the engine control module.
- RPM signal circuit
The engine RPM is detected by the crankshaft position sensor and the signal is input into TERMINAL NE+ of the engine control module.
- Throttle position sensor signal circuit
The throttle position sensor detects the throttle valve opening angle as a control signal, which is input into TERMINALS VTA1 and VTA2 of the engine control module.
- Vehicle speed circuit
The vehicle speed sensor (Combination meter) detects the vehicle speed, and the signal is input into TERMINAL SPD of the engine control module via the combination meter.
- 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 the engine control module start up power supply is applied through the EFI relay, to TERMINALS +B and +B2 of the engine control module. The current from the IGN fuse flows to TERMINAL IGSW of the engine control module, and voltage is constantly applied to TERMINAL +BM.
- Intake air volume signal circuit
The intake air volume is detected by the mass air flow meter, and is input as a control signal to TERMINAL VG of the engine control module.
- 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.
- Starter signal circuit
To confirm whether the engine is cranking, the voltage that is being applied to the starter motor when the engine is cranking is detected, and is input into TERMINAL STA of the engine control module as a control signal.
- Engine knock signal circuit
Engine knocking is detected by the knock sensors, and is input into TERMINALS KNK1 and KNK2 of the engine control module as a control signal.
- 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 AC1 of the engine control module.
- Air fuel ratio signal system
The air fuel ratio is detected by air fuel ratio sensor and input as control signals into TERMINALS A1A+ and A2A+ of engine control module.
- Engine coolant temp. signal circuit
- Control System
* SFI system
The SFI system monitors the engine condition through the signals received from various sensors by the engine control module. Then control signals are output from the engine control module TERMINALS #10, #20, #30, #40, #50, #60, #70 and #80 to operate the injectors (Fuel injection). The SFI system controls the fuel injection via the engine control module in response to the driving conditions.
* ESA system
The ESA system monitors the engine condition through the signals received from various sensors by the engine control module. The best ignition timing is then determined according to this data and the data stored in the engine control module. Then control signals are output from TERMINALS IGT1, IGT2, IGT3, IGT4, IGT5, IGT6, IGT7 and IGT8, and these signals control the igniters to provide the best ignition timing.
* Heated oxygen sensor heater control system
The heated oxygen sensor heater control system turns the heater on when the intake air volume is low (Exhaust emissions temperature is low), and warms up the heated oxygen sensors to improve their detection performance. The engine control module evaluates the signals from each of the sensors, and outputs current from TERMINAL HT1B or HT2B to control the heaters.
* Air fuel ratio sensor heater control system
The air fuel ratio sensor heater control system turns the heater on when the intake air volume is low (Exhaust emissions temperature is low), and warms up the air fuel ratio sensor to improve detection performance of the sensor. The engine control module evaluates the signals from each of the sensors, and current is output to TERMINALS HA1A and HA2A, controlling the heaters.
* Fuel pump control system
The engine control module supplies current to TERMINAL FPR, and controls the operating speed of the fuel pump via the FUEL PUMP relay.
* ACIS
The 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.
* ETCS-i
The ETCS-i optimizes the engine output level in accordance with the opening of the accelerator pedal, under all driving conditions.
* Engine start control system
The engine control module allows power to be supplied from TERMINAL STAR/NSW to the STA relay via the park/neutral position SW until complete combustion is confirmed by the engine RPM after the detection of the ignition SW ST signal by TERMINAL STSW.
With this arrangement, the engine can be started without holding the ignition key in the ST position. At the same time, the TERMINAL ACCR is controlled so that the engine control module turns off the ACC CUT relay, shutting off power to the accessories.
* VVT-i
This system optimizes the intake camshaft valve timing in accordance with the engine condition.
* Air Injection System
This system is designed to improve the exhaust control performance by activating the catalyst at an early stage, which is determined to be when air is pressurized and sent into the exhaust pipe forcibly by the air injection pump at when starting the engine while it is cold.
- 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 on the malfunction indicator lamp.
- Fail-Safe System
When a malfunction has occurred in any system, there is a possibility of causing engine trouble due to continued control based on that system. In that case, the fail-safe system either controls the system using the data (Standard values) recorded in the engine control module memory, or else stops the engine.