System Outline
The engine control system utilizes a microcomputer and maintains overall control of the engine, etc. An outline of the system is given here.
- Input Signals
- Engine coolant temp. signal system
The engine coolant temp. sensor detects the engine coolant temperature and has a built-in thermistor whose resistance varies according to the engine coolant temp. Thus the engine coolant temperature is sent as a control signal to TERMINAL THW of the engine control module.
- Intake air temp. signal system
The intake air temp. sensor is installed in the mass air flow meter and detects the intake air temperature, which is sent as a control signal to TERMINAL THA of the engine control module.
- Oxygen sensor signal circuit
The oxygen density in the exhaust emissions is detected and is input as a control signal 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 then input into TERMINALS VTA1 and VTA2 of the engine control module.
- Vehicle speed circuit
The vehicle speed sensor detects the vehicle speed, and the signal is sent from TERMINAL SP1 of the skid control ECU with actuator, via the combination meter, to TERMINAL SPD of the engine control module.
- 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 which 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.
- Air fuel ratio signal system
The air fuel ratio is detected by the air fuel ratio sensor and input as a control signal into TERMINALS A1A+, A2A+ of engine control module.
- Engine coolant temp. signal system
- Control System
* SFI system
The SFI system monitors the engine condition through the signals received from the various sensors by the engine control module. Then control signals are sent from the engine control module TERMINALS #1, #2, #3, #4, #5, #6, #7 and #8 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 conditions through the signals received from the various sensors by the engine control module. The best ignition timing is 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 (The 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 the sensors, and outputs current from TERMINALS HT1B, HT2B to control the heater.
* 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 (The 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 the sensor, and current is output from TERMINALS HA1A and HA2A, controlling the heater.
* Fuel pump control system
The engine control module supplies current from 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 under all driving conditions to match the accelerator pedal opening.
* Engine start control system
The engine control module allows power to be supplied from TERMINAL STA to the STA relay via the park/neutral position SW until complete combustion is confirmed by 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
The VVT-i optimizes the intake camshaft to valve timing in accordance with the engine conditions.
* Air Injection System
The system is designed to improve the exhaust control performance by activating the catalyst at an early stage, which is detected when air is sent into the exhaust pipe under pressure, from the air injection pump when starting the engine from a cold start.
- 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 may be a possibility of engine trouble being caused from continued control based on that system. In that case, the failsafe system either controls the system using the data (Standard values) recorded in the engine control module memory, or else stops the engine.