Iveco Daily. Manual - part 178
Revi - February 2005
772642
Brake pedal position sensor
There are two of these sensors mounted on the pedal board.
With the brake pedal released, they provide the control unit
with a positive signal that is used to detect brake operation so
as to deactivate the Cruise Control function and stop delivery
of fuel.
In addition, a sensor switches on the brake lights.
764261
Vehicle speed sensor
This sensor, mounted on the gearbox by the drive output
shaft, transmits the vehicle speed signal, through the electronic
tachograph, to the control unit.
ACTUATORS
The injection system comprises three classes of actuators
interlocked with the electronic control unit:
- electro-injectors (see relevant heading);
- regulators (see relevant headings) requiring PWM control
(Pulse Width Modulation):
•
for pressure
•
EGR (if mounted)
•
turbocharger with variable geometry (if mounted);
- actuators with continuous ON/OFF signal to:
•
engage electromagnetic coupling for radiator cooling
fan;
•
turn on/off air-conditioner compressor (if mounted);
•
Cruise Control;
•
starter heater control;
•
fuel filter heating;
•
electric supply pump.
PWM (Pulse Width Modulation) controls
A PWM control has an active and an inactive state that
alternate within a constant set length of time. During the active
state the actuator control circuit is closed, which is thus
powered with the control voltage; whereas, during the
inactive state the circuit is open.
The duration of the two states may be varied with the
condition that the sum of the two times is equal to the length
of the modulation delivery.
The duration of the active state determines the duty-cycle,
which is normally expressed as a percentage of the total time.
Therefore, if the duration of the two active and passive states
are the same, the duty-cycle is equal to 50%.
For reasons of diagnostics, the duty-cycle is limited between
1% and 99%; the control resolution is equal to 0.005%
(1/20000 of the time).
The time length has been chosen taking account of the
dynamic actuator response specifications.
Too low a carrier frequency could cause oscillations in the
actuator, while too high a frequency would decrease control
resolution.
The control of the E.G.R. (if fitted) and the turbocharger with
variable geometry (if fitted) occurs through the idle
modulating valve.
All the power controls are made with relays located
in the cab.
NOTE
772655
Air temperature and pressure sen-
sor
Positioned on the intake manifold, it measures the pressure of
the turbocharging air introduced into the intake manifold.
This value, together with that of the air temperature sensor,
makes it possible for the electronic control unit to calculate the
exact quantity of air introduced into the cylinders so as to
operate the injectors adjusting the fuel delivery, limiting
harmful emissions, improving consumption and performance.
The sensor contains an electronic temperature correction
circuit to optimize the pressure measurement in relation to
the temperature of the intake air.
772656
Fuel temperature sensor
Integrated in the fuel filter, it measures the fuel temperature
and transmits it to the electronic control unit.
When the fuel temperature is too high (ambient temperature
condition, engine at full load and tank in reserve), correct
lubrication of the high-pressure pump is no longer assured. On
the basis of the values received, the control unit determines
the density and volume of the fuel, correcting the delivery
limiting engine performance.
774511
Fuel pressure sensor
It is fitted on the hydraulic accumulator end (rail) and its
function is to transmit a “feed-back” signal to the injection
control unit for:
-
adjust injection pressure
-
adjust the duration of injection.
766161
Atmospheric pressure sensor
This is integrated in the electronic control unit. It provides a
criterion of correction for the measurement of the air flow
rate and to calculate the reference air flow rate to check the
EGR.
764254
Engine coolant temperature sensor
This provides the control unit with an index of the thermal
status of the engine in order to determine corrections for the
fuel delivery, injection pressure, EGR injection advance when
starting cold (if mounted) and warm-up.
505910
Throttle pedal position sensor
The accelerator pedal position sensor provides the control
unit with a voltage value in proportion to the angle of
operation of the pedal determining fuel delivery.
772641
Clutch pedal position sensor
Mounted on the pedal board, it provides the control unit with
a positive signal when the clutch is engaged (pedal released).
Every time the clutch is disengaged to change gear, the control
unit fails to receive this signal and deactivates the Cruise
Control function.
608
F1C ENGINE
D
AILY
Base - May 2004