CAC Gasoline Engine Maintenance And Servicing Manual
79
advance is calculated by a basic chart(pressure, revolution) and trimmed by engine load, water temperature,
and air temperature. In addition, it may perform dynamic ignition advance to stabilize idle speed. Engine idle
speed actuator adjusts the by-pass pipe opening to keep idle value constant . And engine idle actuator is
consisted of linear stepper motor.
Generally, ECU receives input signal and operates output actuating device to integrate idle speed, spray,
ignition’s control. Moreover, HCMOS microprocessor, with wonderful static-prevention and high-speed
calculation ability and low power consumption, may fulfill the following functions:
· the diagnosis for resuming system operation. As a sensor fails, the diagnosis system may resumes the
operation using the stored value preset..
·diagnosis for faulty Actuator condition
·Even if stopped, as a system part fails , the
warning indicator will be energized and the
information of fail type will be stored.
·during service, diagnostic tester may be connected and actuator may be operated to check for failure.
1.“I.A.W 6F……”ECU
Read the square figure (figure 135), ECU processes all sensor signals related with running parameters:
·Intake manifold absolute pressure ·The TDC and revolution of cylinder 1,4 and 2,3
·Throttle valve open position ·Intake air temperature
·Engine coolant temperature · A/C compressor switch signal
·Oxygen (λ) sensor signal (millivolt signal )
By this way, calculate air charge (process absolute pressure, air temperature, speed, and throttle valve position
signal) and use output circuit to control the following:
·control fuel injector switch on time for calculating fuel feed.
·control by-pass air volume and ignition advance for stepper motor compensating to control idle
speed.
·control two high pressure ignition coil, and ignition energy of cylinder 1,4 and 2,3.
·control fuel vapor recirculation solenoid switch on/off
also ECU features a complete self diagnostic for input sensor and output actuator. The diagnosis may be
performed by connecting CHE CK—UP1 with system and the failures detected will be shown on the screen.
For instance:
·all sensor are shorted or opened, including pressure, air, water, throttle valve, λsensor, TDC/RPM sensor
( signal sequence is missing).
·Engine idle speed actuator (stepper motor) doesn’t work.
·stepper motor, fuel injector, and fuel pump circuits are shorted
·high pressure ignition coil, fuel vapor recirculation solenoid is shorted or opened.
main parameters are shown according to the requirements: speed, water temperature, injection time,
ignition advance , intake manifold pressure, throttle valve position, battery voltage, stepper motor
position(steps).
when engine is stopped and ignition switch is on, ECU may perform active diagnostic function, which
may operate ECU microprocessor to check whether the following accessories are running well or not: fuel
pump, fuel injector, and fuel vapor recirculation solenoid. After service, you may erase trouble code stored. To
check stepper motor, technician needs to start the engine before checking.
ECU memory stores a series of emergency parameters for resuming operation. The emergency function
may insure that cars may be drive home or sent to service center. the emergency parameters are indicated by
special LED.
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