13B-12V1 MR-376-X76-13B000$030.mif
DIESEL INJECTION
Fault finding – System operation13B
DCM 1.2 Injection
Program no.: 4C
Vdiag No.: 08
Idling speed regulation
The computer handles the calculation of idling speed. This has to take account of the instantaneous power level to
be supplied, according to the following factors:
– engine coolant temperature,
– gear ratio engaged,
– battery charge,
– electrical consumers (Additional heating, Air conditioning, Fan Unit, electric windows, etc.) active or inactive,
– system faults detected.
Individual injector correction (C2I)
The DCM 1.2 system injectors must be calibrated with correction values so that their flow may be adjusted precisely.
Each injector is calibrated for different pressures on a test bench, and its specifications are shown on a label
attached to the body of the injector holders. These individual correction values are then entered into the computer
EEPROM, which can then control the injectors, taking their manufacturing variations into account.
Measuring the angular position (Cylinder reference sensor)
The angular position is measured using a magneto-inductive sensor triggered by machined teeth on the shaft
flywheel. This flywheel has sixty teeth separated by six degrees minus two missing teeth, that form a notch.
A second sensor (Hall effect) triggered by a machined tooth on the high pressure pump drive pulley (synchronised
with the camshaft), which rotates at half the engine speed, supplies an injection cycle running signal. By comparing
the signals from these two sensors, the computer's APS module (Angular Position Subsystem) is able to supply the
synchronisation components to the system assembly, namely:
– the angular position of the flywheel
– the speed and number of the active injector
– the injection cycle progress.
This module also supplies the system with the engine speed signal.
Flow capacity function (VLC)
Because of the combination of several parameters such as the diesel fuel temperature, part wear, clogging of the
diesel filter etc., the system limit may be reached during its service life. If this happens, the rail pressure cannot be
maintained because the pump lacks the necessary capacity. If the pump lacks the necessary capacity, this
programming will therefore reduce the requested flow to a value that will enable the pressure monitoring system to
control the pressure again.
The customer may have noticed a loss of vehicle performance when this program is activated (confirmed by status
Flow capacity function). This is part of normal operation.
13B-191V1 MR-376-X76-13B000$160.mif
DIESEL INJECTION
Fault finding – Tests13B
DCM 1.2 Injection
Program no.: 4C
Vdiag No.: 08
TEST 6 High pressure system check
NOTESSpecial note:
Certain faults make it impossible to carry out this test - deal with these first.
WARNING
Running the starter motor for more than 5 seconds is dangerous and serves no useful
purpose.
Preliminary Checks:
– Check for the presence of fuel
– Check that there is no air in the low pressure circuit. Apply TEST 1 Low pressure circuit check.
– Ensure that the correct fuel is being used. Apply TEST 13 Diesel fuel conformity check.
The pump's capacity to produce high pressure can be checked by the following procedure:
–With the ignition off, disconnect the low pressure actuator from the pump (IMV brown connector) and
connect a test IMV or the MOT adapter. 1711 adapter.
– Electrically disconnect the four injectors.
– Switch on the ignition, connect the diagnostic tool and re-establish dialogue with the injection system.
– Go to the Main computer statuses and parameters screen.
– Run the test cold, PR064 "Coolant temperature" < 30 °C or equal to ambient temperature.
–Activate the starter for 5 seconds.
– Read the maximum rail pressure value PR038 Rail pressure during the test on the diagnostic tool.
PR038 > 1050 bar?
A
NO
B
YES
DCM1.2_V08_TEST06
