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 temperature signal circuit
The E.F.I. engine coolant temperature 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 input into TERMINAL THW of the ECM as a control signal.
- Intake air temperature signal circuit
The intake air temperature 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 ECM.
- Oxygen sensor signal circuit
The oxygen density in the exhaust emissions is detected and is input as a control signal from the oxygen sensors to TERMINALS OX1B and OX2B of the ECM.
- RPM signal circuit
the engine RPM is detected by the crank position sensor installed in the cylinder block and the signal is input into TERMINAL NE+ of the ECM as a control signal.
- Throttle position sensor signal circuit
The throttle with motor body assembly detects the throttle valve opening angle as a control signal, which is input into TERMINALS VTA1 and VTA2 of the ECM.
- Vehicle speed circuit
The vehicle speed sensor detects the vehicle speed, and the signal is input into TERMINAL SPD of the ECM via the combination meter assembly, from TERMINAL SP1 of the ABS and traction actuator assembly.
- Battery signal circuit
Voltage is constantly applied to TERMINAL BATT of the ECM. When the ignition switch is turned on, the voltage for the ECM start-up power supply is applied to TERMINAL +B and +B2 of ECM via the EFI MAIN relay.
- 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 ECM.
- Stop light switch signal circuit
The stop light switch assembly is used to detect whether the vehicle is braking or not, and the signal is input into TERMINAL STP of the ECM 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 ECM as a control signal.
- Engine knock signal circuit
Engine knocking is detected by the knock control sensors, and is input into TERMINALS KNK1 and KNK2 of the ECM as a control signal.
- Air fuel ratio signal circuit
The air fuel ratio is detected and input as a control signal into TERMINALS A1A+, A2A+ of the ECM.
- Engine coolant temperature signal circuit
- Control System
* SFI system
The SFI system monitors the engine condition through the signals received from various sensors by the ECM. Then control signals are sent from the ECM TERMINALS #10, #20, #30, #40, #50, #60, #70 and #80 to operate the fuel injector assembly (Fuel injection). The SFI system controls the fuel injection by the ECM in response to the driving conditions.
* ESA system
The ESA system monitors the engine condition through the signals received from various sensors by the ECM. The best ignition timing is determined according to this data and the data stored in the ECM. 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.
* Oxygen sensor heater control system
The oxygen sensor heater control system turns the heater on when the intake air volume is low (Temperature of exhaust emissions is low), and warms up the oxygen sensors to improve their detection performance. The ECM evaluates the signals from each sensor, and outputs current to TERMINALS HT1B or 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 (Temperature of exhaust emissions is low), and warms up the air fuel ratio sensor to improve detection performance of the sensor. The ECM evaluates the signals from each sensor, and current is output to TERMINALS HA1A and HA2A, controlling the heater.
* 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 in accordance with the accelerator pedal opening, under all driving conditions.
* VVT-i
VVT-i controls the intake valve timing to the most appropriate levels in accordance with the engine conditions.
- Diagnosis System
If there is a malfunction in the ECM 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
If 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 ECM memory, or else stops the engine.