Electronic control system
2-9
ISC valve control
The engine ECM adjusts the opening of the ISC valve so that engine speed is maintained at a target
value when the throttle valve is fully closed.
Knock control
The engine ECM receives a knock signal from the knock sensor that is installed to the cylinder block.
To protect the engine from damage, the engine ECM retards the ignition timing and decreases the en-
gine speed according to the amount of knocking.
If the knocking occurs frequently, the ignition timing is
retarded until knocking is no longer detected, and
the retarded ignition timing is maintained, using the learning function.
Regardless of the preceding conditions,
the knock control also activates when the thermo sensor is
malfunctioning.
Battery removal control
If the battery terminal has been removed, the fuel injection and ignition for all cylinders are shut-off to
stop the engine and protect the rectifier/regulator.
Fail-safe
In the fail-safe control, the engine ECM enters the fail-safe control mode when an electrical component
malfunctions.
The fail-safe control system records the trouble codes according to the engine trouble conditions.
Water temperature
Engine speed 53 C (127.4 F) o
r less More than 53 C (127.4 F)
More than 500 r/min Knock control does not activate Knock control activates
Trouble
code
Item
Trouble conditions to be
dete
cted
Control and operation
15 Thermo sensor
Open or short circuit in the
ther
mo sensor circuit.
Output voltage is less than 0.1
V or more th
an 4.5 V.
Control is performed based on
the intak
e air temperature
when starting.
Set to 40 C (104 F) whe
n
running.
High engine idle speed.
17 Knock sensor
Short or open circuit in the
knoc
k sensor circuit.
Output voltage is less than 0.9
V or more th
an 4.0 V.
Ignition timing is retarded.
18 TPS
Open or short circuit in the
TPS circuit.
Output voltage is less than 0.3
V or more th
an 4.7 V.
Control is performed based on
the
intake air pressure.
19 Battery voltage
Voltage is 12 V or less for 2
min
utes, even when engine
speed is 2000 r/min or more.
High engine idle speed.
23
Air temperature sen-
sor
Open or short circuit in the air
temper
ature sensor circuit.
Output voltage is less than 0.1
V or more th
an 4.6 V.
Set to 40 C (104 F).
High engine idle speed.
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