The common rail fuel injection system consists of sensors which detect the condition of
the diesel engine, an engine electronic control unit (engine-ECU) which controls the system
based on signals from these sensors, and actuators which operate according to control commands
from the engine-ECU. The engine-ECU carries out activities such as fuel injection control and
idle speed control. In addition, the engine-ECU is equipped with several self-diagnosis functions
which make troubleshooting easier in the event that a problem develops.
FUEL INJECTION CONTROL
The injector drive time, the injection timing and the fuel pressure are controlled so
that the appropriate quantities of fuel are supplied to the engine in response to engine conditions
which can change frequently. A single injector is mounted at each cylinder. The supply pump
increases the fuel pressure to the pressure which is required for high-pressure injection, and
then send the fuel each injector.
IDLE SPEED CONTROL
The idle speed is kept at the optimum speed by controlling the fuel injection quantity
in accordance with changes in idling conditions and engine load during idling. The engine-ECU drives the fuel injector to keep the engine running at the pre-set idle
target speed in accordance with the engine coolant temperature and A/C and other electrical
load.
SELF-DIAGNOSIS FUNCTION
When an abnormality is detected in any of the sensors or actuators, the engine
warning lamp illuminates to warn the driver.
When an abnormality is detected in any of the sensors or actuators, a diagnosis
code number corresponding to the problem which occurred is output.
The RAM data relating to the sensors and actuators which is stored in the engine-ECU
can be read using the M.U.T.-III. In addition, the actuator can be force-driven under certain conditions.
OTHER CONTROL FUNCTIONS
Power Supply Control When the ignition switch ON signal is input by the ignition switch, the engine-ECU turns
ON the power transistor for controlling the engine control relay. As a result, current flows
through the coil in the engine control relay, causing the relay switch to turn ON and supply
power to the sensors and actuators.
Glow Control Refer to GROUP 16 (Refer to , GROUP 16 - Glow System).
EGR Control Refer to GROUP 17 [Refer to , GROUP 17 - Engine And Emission
Control - Exhaust Gas Recirculation (EGR) System].
A/C Relay Control Turns the compressor clutch of the A/C ON and OFF.
Condenser Fan Motor Relay Control Controls the condenser fan motor relay based on the A/C switch, A/C load signal, engine
coolant temperature and vehicle speed input signals.
PTC Heater Relay Control <Vehicle with PTC heater> The PTC heater is turned ON is accordance with the A/C operation at the engine cold state.
FUEL INJECTION SYSTEM DIAGRAM
<Vehicles with filter pressure switch> <Vehicles without filter pressure switch>