2000 RENAULT SCENIC engine

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Injection/air conditioning programming
13
13-14
Injection/air conditioning programming
INJECTION COMPUTER/AC COMPUTER CONNECTION
The compressor is of the variable cubic capacity type.
The injection calculator and the air conditioning calculator are linked by two leads:
– The power absorbed information tells the injection computer the output absorbed by the compressor. It is possible
to see the output absorbed using the diagnostic tool. When air conditioning is engaged the reading should be
between 250 and 5000 Watts.
– The connection from the injection computer to the air conditioning computer. This lead carries information on
whether starting the compressor is authorized or forbidden.
When the air conditioning function is selected, idling speed is modified to reach a maximum of 875 rpm.
IMPORTANT: the absorbed output is never equal to 0, whatever the status of the compressor, engaged or not. The
minimum value read is approximately 250 Watts.

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Injection/air conditioning programming
13
13-15
COMPRESSOR OPERATION PROGRAMMING
During certain stages of operation, the diesel injection computer stops the compressor from functioning.
Engine start programming
The compressor is prevented from operating for 5 seconds after the engine has started.
Recovery of performance
When the position of the accelerator pedal is changed significantly and if the engine speed is less than 3000 rpm,
the compressor is prevented from operation for 5 seconds.
Recovery of output when the vehicle starts moving
If the position of the potentiometer is more than 50 % the engine speed is less than 2250 rpm and the vehicle speed
is below 20 km/h, the compressor is cut for 5 seconds.
Anti-stall protection
If the no load position is not detected, and the engine speed is less than 675 rpm. the compressor is disengaged. It
is engaged again after 5 seconds if the engine speed is increased.
Thermal protection programming
The compressor does not engage in cases where the coolant temperature is greater than + 112 °C.

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Idle speed correction
13
13-16
Idle speed correction
IDLING SPEED CORRECTION ACCORDING TO COOLANT TEMPERATURE
CORRECTION OF THE IDLING SPEED WHEN THE POTENTIOMETER IS FAULTY
If the accelerator pedal potentiometer is faulty, idling speed is held at 1200 rpm.
If the information from the accelerator pedal position potentiometer and the brake switch information does not
correspond, the speed is changed to 1250 rpm.
CORRECTION OF THE IDLING SPEED ACCORDING TO THE GEAR RATIOS
The running idling speed is modified according to the gear engaged in the gearbox:
– in 1
st, 2nd and 3rd gears the speed is 835 rpm.,
– for other gears the speed is 925 rpm.

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Pre-postheating control
13
13-17
Pre-postheating control
The pre-postheating function is controlled by the preheating unit.
OPERATING PRINCIPLE FOR PRE-POST HEATING
1) "Preheating" on ignition
a) Variable preheating
The warning light lighting time and the
supply to heater plugs time depends on the
coolant temperature and the battery
voltage.
In all cases the injection warning light
lighting time cannot exceed 15 seconds.
b) Fixed preheating
After the warning light goes out the plugs
remain supplied for a fixed period of
10 seconds.2) Starting
The plugs remain supplied while the starter is
being activated.
3) "Postheating" while the engine is running
During this phase the plugs are supplied
continuously according to coolant temperature.
time (s)
Coolant
temperature °C For idling speed without
depression of the accelerator
pedal.

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Heater plugs
13
13-18
Heater plugs
The resistance of a heater plug is 0.6 Ω.
Plugs may be removed without having to open the
high pressure circuit.
REMOVAL
Unclip the plug connector.
Clean the plug exterior to avoid any dirt entering the
cylinder.
Undo and then remove the plugs.
To undo the plug on cylinder 4 use a 10 mm long radio
socket attached to a universal joint. Once the plug is
loosened use a pipe socket to unscrew it completely.
REFITTING
Proceed in the reverse order to removal.TIGHTENING TORQUES (in daN.m)
Heater plug 1.5
15762S

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Thermal plunger
13
13-19
Thermal plunger
The three thermal plungers are located on a water unit
fixed under the manifold at the engine - gearbox joint.
The objective of the system is to reheat the coolant.
The thermal plungers are supplied with 12 volts by
two relays. One relay controls two thermal plungers,
and the other relay controls one thermal plunger. This
enables control of one, two or three thermal plungers
as required.
The resistance of the thermal plungers is:
0.45 ± 0.05 Ω at 20˚C. Control strategy
When the thermal plungers are operating the idling
speed is brought to 900 rpm.
Thermal plungers cannot operate in the case of:
– preheating,
– post heating,
– heated windscreen selected,
– engine speed below 700 rpm.,
If the conditions mentioned above apply, the thermal
plungers are controlled according to a characteristics
map linked to the air and coolant temperature.
Unshaded zone: Thermal plunger not supplied
Shaded zone: Thermal plunger supplied

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Thermal plunger
13
13-20
If the battery voltage is > 13.5 volts
if not then
Thermal plungers
not suppliedOne thermal plunger
supplied
If after 20 seconds the battery
voltage is
> 13.5 volts
if not then
Thermal plungers
not suppliedTwo thermal plungers
supplied
If after 20 seconds
the battery voltage is
> 13.5 volts
if not then
Thermal plungers
not suppliedThree thermal plungers
supplied if the battery
voltage is
> 13.5 volts and if the
conditions mentioned above
are fulfilled

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Low pressure pump (supercharging pump)
13
13-21
Low pressure pump (supercharging pump)
The supercharging pump is an electric pump located in
the engine compartment.
REMOVAL
IMPORTANT: take note of the quantity of diesel and
the residual pressure in the pipes.IMPORTANT:
A fuel cock (R) is fitted to the fuel filter at the level of
the return pipe leading to the tank.
It should be in open position for normal operation.
To reprime the circuit after an intervention, a filter
change or a fuel fault you should:
– close the fuel cock (R),
– start the low pressure pump by switching on the
ignition several times,
– start the engine,
– OPEN THE FUEL COCK (the valve is open when the
two coloured lines are aligned).
NOTE: certain vehicles are not fitted with a fuel cock.
In this case, ignore this operation. YOU SHOULD FOLLOW THE CLEANNESS
INSTRUCTIONS CLOSELY.
16776S
16870R3