ENGINE FUEL AND EMISSION CONTROL SYSTEM 6C-45
Actuators
The injection system includes three categories of actuators linked
to the electronic control unit:
A) Electro-injectors (see corresponding chapter)
B) Regulators requiring a PWM (Pulse Width Modulation) con-
trol:
• Fuel pressure
• EGR (if fitted)
• Variable geometry turbocompressor (if fitted)
C) Actuators with a continuous ON/OFF signal for:
• Electromagnetic connection joint for radiator cooling fan
• Stop/start for air-conditioning compressor (if fitted)
• Cruise control (if fitted)
• Fuel heater in filter
• Electric feed pump
NOTE:
The power controls are composed of relays
PWM (Pulse Width Modulation) Controls
A PWM control presents an active state and an inactive one
which alternate within a pre-established and constant period.
During the active state, the control circuit is closed for that atuator
supplied with tension. During the inactive state, the circuit is
open.
The duration of the two states can be varied as long as the sum
of the two durations is the same as the flow modulation period.
The duration of the active state determines the "duty-cycle" which
is normally represented as a percentage of the total period; for
example, if the duration of the two active and inactive states is
equal, the duty-cycle will be 50%.
For reasons of diagnosis, the duty-cycle is limited between 1
and 99%, the control resolution is equal to 0.005% (1/20000 of
the period).
The duration of the period is chosen noting control response
dynamic characteristics.
If the frequency is too low, oscillations in the operator can occur,
whereas if the frequency is too high, the operator resolution is
reduced.
Blink - code
With the ignition off, press the diagnosis button:
- Two series of EDC warning light flashing, separated by a
brief pause, indicate the code of the first error memorised.
- Press the button again to move on to the next error.
- When the last error is reached, the first is repeated.
- The error list contains all the memorised errors, not just the
active ones.
- The order of error presentation respects the chronological
order in which they have occurred.
- To erase the list of errors from the control board memory,
follow the procedure:
• With the ignition off, press the diagnosis button.
• With the button still depressed, put on the ignition.
• Keep the button depressed for 5 seconds.
• Release the button.
• Switch off the ignition.
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