13B-13V1 MR-376-X76-13B000$030.mif
DIESEL INJECTION
Fault finding – System operation13B
DCM 1.2 Injection
Program no.: 4C
Vdiag No.: 08
Function: Air flow management
EGR valve control
The EGR system (Exhaust gas recirculation) comprises a proportional EGR valve, with a built-in valve position
feedback potentiometer. The EGR valve position is controlled by the potentiometer in a closed loop and/or by
changes in the estimated air flow.
Special feature of the K9K796 Euro 2 engine (Indonesia): The EGR solenoid valve is present on the vehicle, but not
used. It always remains closed. It must not be replaced on this vehicle (unless there is a mechanical fault).
Calculating the air flow
K9K 790 and 794 engines are not fitted with an air flowmeter. Instead, the amount of fresh inlet air is evaluated
based on the values supplied by the surrounding systems.
The (theoretical) air load is calculated using a model with various calculation parameters, which are:
– the inlet air temperature measured by a sensor located after the turbocharger and/or after the exchanger (if fitted),
– the turbocharging pressure,
– the atmospheric pressure (external air),
– the EGR valve position,
– the fuel flow,
– the engine speed.
The atmospheric pressure sensor is optional. If fitted, it sends back a signal relating to the atmospheric pressure to
an analogue port on the micro-controller. If not, atmospheric pressure is recovered based on the turbocharger
pressure and the engine field.
For K9K 792 and 796 engines, the flow of fresh air entering the engine is measured by a hot-wire ratiometric sensor.
This flowmeter is used to manage the amount of exhaust gas to be recirculated to ensure optimum recirculation
rates. A fresh air temperature sensor is integrated into the flowmeter. Air flow measurement allows closed-loop
control via the EGR valve.
Turbocharger control
K9K 796 engine:
The turbocharging system is made up of a solenoid valve which is used to control the wastegate to adjust the
absolute pressure of the inlet circuit.
K9K 790, 792, 794 engines:
The turbocharger system is controlled by the inlet pressure and does not need to be controlled by the computer.
Pre-postheating actuation
Pre-postheating actuation consists of controlling the heater plugs and the preheating warning light on the instrument
panel. The heater plugs are activated by a preheating unit (controlled by the injection computer), and the power is
supplied by the battery. After the ignition is switched on a preheating delay is activated. The indicator light comes on
for the activation period which is dependent on the battery voltage, atmospheric pressure and coolant temperature.
If the temperature is below a certain threshold, a postheating function can be used to improve the combustion
stability, and consequently engine operation (reducing unburnt particles and pollutant emissions).
