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Actuators
• Devices that allow the computer to do work and alter the
operation of other components.
• Actuators can be: Solenoid, relay , servo motor, display
device and control module.
• When the computer turns on an actuator, it normally
provides the device with a ground circuit, Current can
then operate the actuator.
• Common actuators used on modern vehicles include:
– Fuel injector: solenoid valve that controls fuel flow
– Fuel pump: electric motor-driven pump
– Idle speed control valve: controls airflow into the
engine to control idle speed
– EGR solenoids: open and close small ports to control
exhaust gas flow back into the engine.
– Ignition coil: changes low voltage into high voltage that
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 EDC injector
• These electromechanical diesel fuel injectors
contain a solenoid controlled by the ECM to
manage fuel timing and metering.
• The ECM injector driver circuitry supplies high
voltage to the injector solenoids which are
energized by controlling the ground circuits
within the ECM.
• Injector calibration codes need to be
programmed into the ECM to compensate for
manufacturing tolerances.
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 Engine Cooling Fan Solenoid
• When energized by the ECM, this normally closed
solenoid supplies air pressure to disengage the engine
cooling fan clutch and turn the fan OFF.
• The solenoid can be de-energized by the ECM, shutting
off air pressure to engage the fan clutch and turn the fan
ON.
• The ECM engages the fan to assist with engine braking
when the selector switch is in the HIGH position.
• The ECM will operate the fan for engine protection when
coolant temperature reaches 205ºF, engine oil
temperature at 245ºF, intake manifold temperature at
190ºF, and when the A/C high-pressure switch opens.

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 Stop Engine Lamp
• The red stop engine lamp (SEL) illuminates when the engine
protection system is in the de-rate and shutdown modes.
• The red SEL can also be used to read active fault “flash” codes
when in the diagnostic mode.

Check Engine Lamp

• The amber/yellow check engine lamp (CEL) illuminates when
the engine protection system is in the warning mode, or when
electronic control system failures are occurring and inactive
fault is present.
• The yellow CEL can also be used to read inactive fault “flash”
codes when in the diagnostic mode.

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 Engine Brake Solenoids
• Three solenoids can be energized by the ECM to
provide engine braking on two, four or all six
cylinders.
• The engine brake can be activated during cruise
control operation.
– The solenoids will be energized after the set speed has
been exceeded,
– when the service brake pedal is depressed
• The ECM will not energize the solenoids when the
clutch pedal is depressed.
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 Fuel pump control
I. On-off control by engine ECU

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II. On-off control by fuel pump switch operated by
vane type air flow meter

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 Gasoline injectors

i. High resistance type ii. Low resistance type

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 Cold start injector
• Injects additional fuel during cranking when the coolant
temperature is low.
• It is controlled by cold start time switch or ECU

Cranking when the coolant Cranking when the coolant

temperature is low temperature is hot
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 Idle speed control (ISC)
• The ISC system controls the idle speed by
means of the ISC valve to change the volume
of air flowing through the throttle valve by
pass in accordance with signals from the
ECU.
• There are four types of ISC valve:
1. Duty ACV (air control valve)
2. Rotary solenoid type
3. Stepper motor type
4. On-off control VSV (Vacuum switching valve)

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• While current flows according to signals from the engine
ECU, the coil becomes excited and the valve moves.
• This changes the gap between the solenoid valve and
the valve body, controlling the idle speed, when the idle
speed is lower than the specified because of different
loads, such as:
– shifting gear,
– switching air condition,
– power steering,
– head light etc.
• The position of the solenoid valve is determined by
the proportion of time that the signal is on as compared
to the time it is off (i.e. by the duty ratio).
• The valve opens wider the longer current flows to the
coil.
• During cranking, STA goes on, causing the ACV to open fully.
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 Duty ratio  ontime
Ontime
offtime

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 2. ROTARY SOLENOID TYPE ISCV
• The valve assembly consists of:
– two electrical coils,
– a permanent magnet,
– a valve and valve shaft.
• The ECU is designed to cause current to flow alternatively in
coil T1 when the duty cycle signal is low and the coil T2 when
the signal is high. By varying the duty ratio.
• The change in magnetic field causes the valve shaft to rotate.
• A fail-safe bi-metallic coil is fitted to the end of the shaft to
operate the valve in the event of electrical failure in the ISCV
system.
• If disconnected or the valve fails electrically the shaft will
rotate to a position which balances the magnetic force of the
permanent magnet with the iron core of the coils.
– This default rpm will be around 1000 to 1200 rpm once the
engine has reached normal operating temperature.

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 3. STEPPER MOTOR TYPE
• The ISC valve has 125 steps from the fully closed to the fully open
position.
• The valve shaft is screwed into the rotor.
• The shaft is prevented from turning by means of a stopper plate, so it
moves in and out as the rotor rotates.
• Decreasing or increasing the clearance between the valve and valve
seat regulates the amount of air allowed through the bypass.
• Each time current passes through the coils the rotor is rotated about
11° (1/32 of a revolution).

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 Stepper motor type ISCV connection to the ECU
• When the ECU judges from the throttle valve opening angle and vehicle speed signals
that the engine is idling, it switches on Tr1 to Tr4, in order, in accordance with the output
of those signals.
• This sends current to the ISC valve coil, until the target idling speed is reached.
• When the engine is stopped (no NE signal to the ECU), the ISC valve opens fully (to the
125th step) to improve startability when the engine is restarted.

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 4. ON-OFF CONTROL VACUUM SWITCHING
VALVE (VSV)

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a. Off to On
• When the engine is cranking and immediately after starting.
• When engine speed falls below a predetermined rpm
• Several seconds after shifting from “P” or “N” into any other
range.
• The light control switch is turned on.
• The rear window defogger switch is turned on.
• If the light control switch or rear window defogger switch is
turned on, the VSV goes on.
b. On to Off
• When a predetermined period of time has elapsed after the
engine has started.
• When engine speed rises above a predetermined rpm.
• After a set time has elapsed after the transmission is shifted
from “P” or “N” into any other range and the engine speed is
above a predetermined rpm with the idle contact on and the
A/C magnetic clutch disengaged.
• The light control switch is turned off.
• The rear window defogger switch is turned off.
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• This type of sensor is known as a heated exhaust gas oxygen
sensor (HEGO).
• Heats up the sensor so quickly that it has already
reached operating temperature in 20-30 sec after engine
has started.
• The Engine ECU controls the operation of the oxygen sensor
heater according to the intake air volume and engine speed:
– When the engine load is small and the exhaust gas temperature is
consequently low, this heater is operated to maintain sensor
efficiency.
– When the engine load and exhaust gas temperature increases greatly,
heater operation is stopped to prevent deterioration of the sensor.

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• PCM-controlled EGR valves are typically vacuum or electrically
operated.
• When vacuum operated, the system looks at the pressure drop across
the metering orifice in the exhaust feed tube or the valve as the valve
opens and closes.
• At the orifice is a differential pressure feedback EGR sensor that sends
a signal to the PCM.

 This is called the differential pressure

feedback EGR (DPFE)system.

EVR: EGR Vacuum Regulator solenoid

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An EGR system with a DPFE sensor.
• In this system, the PCM calculates the desired amount of EGR flow
according to the current operating conditions. The PCM looks at the
inputs from many sensors before determining this value. It then
calculates the necessary pressure drop across the orifice to obtain this
flow. Once the value is determined, the PCM sends commands to the
EGR vacuum regulator solenoid. The solenoid is duty cycled by the
PCM. As the duty cycle increases, more vacuum is sent to the valve and
it remains open for longer periods.
• As exhaust gases pass through the valve, they must also pass through
the orifice. The DPFE sensor measures the pressure drop across the
orifice and sends a feedback signal to the PCM. Based on this signal,
the PCM can make corrections to the operation of the EGR valve.
Normally the voltage signal from the DPFE sensor is 0 to 5 volts and
the voltage is directly proportional to the pressure drop.
• Some EGR valves have an exhaust gas temperature sensor. This sensor
contains an NTC thermistor; an increase in exhaust temperature
decreases the sensor’s resistance. Two wires are connected from the
temperature sensor to the PCM. The PCM senses the voltage drop
across this sensor. Cool exhaust temperature and higher sensor
resistance cause a high-voltage signal to the PCM, whereas hot exhaust
temperature and low sensor resistance result in a low-voltage signal.

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 EGR cut-off control
• The engine ECU actuates the VSV shutting off the
EGR when:
– the coolant temperature is below a predetermined
temperature
– the engine speed is above 4500 rpm to maintain drivability.
– the intake air is above predetermined level
– the fuel cut off function.

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 Electronically Controlled Turbocharging Systems

• Exhaust driven supercharger

• Boost pressure increases with load
• System parts
 Turbocharger
 Intercooler
 Wastegate
 Bypass Valve
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 Wastegate & Bypass Valve
• Wastegate • Bypass Valve: Blow Off Valve
(BOV)
– Controls boost under load
– Controls boost when the throttle
– Redirects exhaust gases around is closed
the turbine
– Releases boost pressure
• Back into the exhaust
system  Back into the compressor
inlet after the MAF
• Out to atmosphere
 Out to atmosphere
– Controlled by boost pressure
– Controlled by manifold vacuum

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Wastegate actuator Bypass Valve actuator
• Solenoid controls the boost
pressure reaching the bypass
valve

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 Turbocharging pressure control

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 EDC controlled glow plug

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 Exhaust system with oxidation type catalytic
convertor and particulate filter with additive system

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 ELECTRONIC IGNITION

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 I. Electronic spark advance (ESA)

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 II. Variable spark timing (VAST)

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 1. Distributor ignition (DI)
system

• Separate type ( ignition coil and Igniter

are located outside distributor).
• Integrated type (ignition coil and Igniter
are located inside distributor).

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 2. Distributorless ignition system (DLI)

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 DLI

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 3. Direct ignition system (DIS)
a. Independent ignition

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 3. Direct ignition system (DIS)
b. Integrated Igniter

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 IG Primary Pattern

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 IG Secondary Pattern

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