tow RENAULT SCENIC 2012 J95 / 3.G Engine And Peripherals EDC16CP33 Workshop Manual

13B-16V12 MR-372-J84-13B300$030.mif
DIESEL INJECTION
Fault finding – System operation13B
EDC16CP33
Program No.: C4
Vdiag No.: 04, 08, 18, 1C,
20, 24, 26, 28, 34, 38, 44,
4C, 54, 58, 5C, 60, 62, 74
III - Management of the damper valve
The damper valve is now responsible for two functions:
– Damping: when the engine is switched off, the flap closes in order to block the passage of air towards the cylinders.
The aim of this is to stop the engine as quickly as possible and to reduce instabilities when the engine is switched
off.
– "Valving" function depending on the engine operation: the damper valve closes by a few % to create a "venturi"
effect at the EGR valve passage section.
The aim of this is to accelerate the air flow of EGR gases and to reduce the emission of pollutants.
IV - Exhaust gas recirculation management
The EGR (Exhaust Gas Recirculation) system involves removing exhaust gases and reintroducing them into the
inlet.
This system plays a major role in reducing diesel engine emissions. The EGR system is cooled by a gas - water
exchanger, as on most Euro IV engines. This cooler has a dual position bypass valve, which allows the gas to be
cooled or not depending on the emission control requirements. The bypass circuit is inside the cooler (not visible
from the outside). The valve control rod is visible from the outside.
The exhaust gases are collected in the exhaust manifold (before the turbocharger), then directed to the EGR cooler
and the EGR valve. The EGR valve connects the air circuit between the damper valve and the inlet manifold; the
EGR valve is positioned next to the damper valve.
The EGR valve is activated every time the engine stops by performing 10opening/closing cycles. This programming
activates the EGR valve in order to prevent it from clogging. The program is no longer active if there are any system
faults.
The EGR system does not operate below 5°C (air flowmeter temperature).
– The controlled EGR cooler bypass
The EGR cooler bypass is controlled by an all-or-nothing solenoid valve, connected on one side to the vacuum
pump, and on the other side to the bypass control diaphragm. It is actuated according to the coolant temperature
and the engine operating status. Gases flow into the EGR section of the cooler unless the engine is cold, in which
case they flow through the bypass valve. There is also a regular actuation function for the bypass valve to prevent it
from clogging.
– EGR valve
The EGR valve is supplied by direct current and connected to a potentiometer copying the position of the valve.
The opening of the valve is actuated (H bridge) by a positive command 0 to 100%.
The valve is controlled using a double regulation loop.
The first loop (fastest) is a position loop. It brings the valve to the desired position by a loop connection using the
signal from the position sensor.
The second loop is slower and is an air flow loop. At a given operating point, the air flow setpoint is attained by
adjusting the quantity of exhaust gas flowing through the EGR valve and the flow of fresh air passing through the
damper valve. At a total constant flow, the more exhaust gas recirculation, the less fresh air there is and vice versa.
The air flow is measured by the flowmeter and the setpoint is attained using both the EGR valve position setpoint
and the damper valve position setpoint.