SYSTEM
EC9-35
< SYSTEM DESCRIPTION >
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When the engine coolant temperature continues to increase and exceeds the alert threshold, ECM judges the
engine is over temperature.
In case of an abnormally high engine coolant temperature, the maximum engine torque is reduced; the driver
will then feel a lack of engine power.
When the engine is not running
Only a FAN1 activation request can be sent for anti-percolation purpose (engine stopped with high engine
coolant temperature). The anti-percolation function is active after ignition switch OFF for a defined maximum
time. At ignition switch OFF, a FAN1 activation request is sent if the engine coolant temperature exceeds
specified temperature and a cutting request is sent when the engine coolant temperature becomes lower.
When there is a default on the engine coolant temperature signal, the FAN1 activation is permanently
requested (engine running).
In addition to this, depending on the equipment mounted on the vehicle, the ECM can also send an activation
request for air conditioning needs or automatic transmission needs or DPF (Diesel Particulate Filter) regener-
ation needs.
THERMOSTAT CONTROL
THERMOSTAT CONTROL : System Description
INFOID:0000000010308984
SYSTEM DRAWING
For system drawing of the thermostat control, Refer to
CO-85, "Engine Cooling System"
.
DESCRIPTION
This engine has an engine coolant bypass valve and a thermoplunger and uses them for improving a warm-up
time.
Thermoplunger
The thermoplunger is installed to the engine coolant line and directly warms up engine coolant.
ECM transmits a thermoplunger operating signal to the thermoplunger control unit when engine coolant tem-
perature is low.
The thermoplunger control unit applies power to the thermoplunger according to the received signal and
warms up engine coolant.
In addition, ECM activates the thermoplunger during DPF (Diesel Particulate Filter) regeneration and
increases electric load for get more engine load to perform normal DPF regeneration.
ECM controls thermoplunger based on the following information.
• Engine coolant temperature
• Battery voltage
• Engine speed
• Alternator load
Engine Coolant Bypass Valve
The engine coolant bypass valve circulates engine coolant within a narrow range and accelerates a warm-up
by closing the valve and cutting off the engine coolant passage.
ECM applies power to the engine coolant bypass valve control solenoid valve when engine coolant tempera-
ture is low.
The engine coolant bypass valve control solenoid valve switches the passage of negative pressure (vacuum)
sent from the vacuum pump. When power is applied to the solenoid valve, negative pressure is applied to the
engine coolant bypass valve. Accordingly, the engine coolant bypass valve closes.
GLOW CONTROL
GLOW CONTROL : System Description
INFOID:0000000010308985
SYSTEM DESCRIPTION
Glow control system operates at engine starting and after engine starting. The system energizes glow plug
according to engine coolant temperature to improve engine starting function.
When the ignition switch is turned ON, the glow control system starts Pre-glow and the glow indicator lamp
turns ON. When the engine starts, the glow indicator lamp turns OFF and the glow control state changes to
After-glow.
Glow time varies according to engine coolant temperature, barometric pressure and battery voltage.
AUTOMATIC SPEED CONTROL DEVICE (ASCD)