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.
- 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 to TERMINAL THA of the engine control module as a control signal.
- Oxygen sensor signal circuit
The oxygen density in the exhaust emissions is detected and is input from the heated oxygen sensors to TERMINAL OX1B of the engine control module as a control signal.
- 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 VTA and VTA2 of the engine control module.
- Vehicle speed signal circuit
ABS speed sensor detects vehicle speed and the speed signal is input from skid control ECU to engine control module.
- Battery signal circuit
Voltage is constantly applied to TERMINAL BATT of the engine control module. When the power SW is pushed on, the voltage for engine control module start up power supply is applied through the EFI M relay, to TERMINAL +B 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 to TERMINAL VG of the engine control module as a control signal.
- Water temp. (CHS) signal circuit
The water temp. (CHS) sensor detects the water temperature (CHS) and has a built-in thermistor whose resistance varies according to the water temperature (CHS). The water temperature (CHS) is then input into TERMINAL THW2 of the engine control module as a control signal.
- Engine knock signal circuit
Engine knocking is detected by the knock sensor, and is input into TERMINAL KNK1 of the engine control module as a control signal.
- Air fuel ratio signal circuit
The air fuel ratio is detected and input into TERMINAL A1A+ of the engine control module as a control signal.
- Engine coolant temp. signal circuit
- Control System
* SFI system
The SFI system monitors the engine condition through the signals received from the various sensors by the engine control module. Control signals are then output from the engine control module TERMINALS #10, #20, #30 and #40 to operate the injectors (Fuel injection). The SFI system controls the fuel injection via the engine control module according 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 determined according to this data and the data stored in the engine control module.
Control signals are then output from TERMINALS IGT1, IGT2, IGT3 and IGT4, and these signals control the igniters to provide the best ignition timing.
* Heater control system of heated oxygen sensor
The heater control system of heated oxygen sensor 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 detecting performance. The engine control module evaluates the signals from each of the sensors, and outputs current to TERMINAL HT1B to control the heater.
* Heater control system of air fuel ratio sensor
The heater control system of air fuel ratio sensor 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 detecting performance of the sensor.
The engine control module evaluates the signals from the sensor, and current is output to TERMINAL HA1A, controlling the heater.
* Fuel pump control system
The engine control module supplies current to TERMINAL FC, and controls the operation of the fuel pump with the C/OPN relay.
* VVT-i
The VVT-i system optimizes the intake camshaft valve timing in accordance with the engine conditions.
* CHS system
The engine control module controls the CHS W/P relay to run the electric pump to supply heated water stored in the CHS tank to the engine head. The electric pump stops when the water reaches a certain temperature or a certain amount of time goes by. Warming the engine head optimizes combustion conditions when the engine is starting, in order to reduce the emission of incomplete combustion gas.
- Diagnosis System
When there is malfunction in the engine control module signal system, the malfunctioning system is recorded in the memory. The system can be found by reading the code displayed on the malfunction indicator lamp.
- Fail-Safe System
When malfunction has occurred in any system, there is possibility of engine trouble due to continuous control based on that system. In such a case, the fail-safe system either controls the system using the data (Standard values) recorded in the engine control module memory, or stops the engine.