Mercedes-Benz ML320. Manual — part 386
ANTI-KNOCK CONTROL FUNCTION - GF15.12-P-4024F
ENGINE 104.941 /943 /944 /991 /994 as of 1.8.96
ENGINE 104.995
with CODE (494a) USA version
with CODE (807) Model year 1997
with CODE (808) Model year 1998
with CODE (498) as of Model Year 97 Japanese version
ENGINE 111.921 /942 as of 1.9.98,
111.943,
111.944 as of 1.8.96,
111.946 as of 1.6.98,
111.947/973,
111.975 as of 1.8.96
ENGINE 111.945
in MODEL 208.335 /435 as of 1.6.98,
202.020/080 as of 1.9.98
ENGINE 111.974
with CODE (494a) USA version
with CODE (807) Model year 1997
with CODE (808) Model year 1998
ENGINE 111.951 /952 /955 /956 /957 /958 /982 /983
ENGINE
Model 211, 230
GF42.45-P-4500SL
ETC control unit, location/task
Transmission 722.6
GF27.19-P-4012G
2001 Mercedes-Benz ML320
1998-2005 ENGINE Electrical System - Engine - 163 Chassis
me
112.910 /911 /912 /913 /914 /916 /917 /920 /921 /922 /923 /940 /941 /942 /943 /944 /946 /947 /949 /953 /954 /95
ENGINE 113.940 /941 /942 /943 /948 /960 /961 /963 /965 /966 /967 /969
ENGINE 119.980 /981 /982 /985
ENGINE 120.982/983
ENGINE 137.970
Fig. 15: Identifying Anti-Knock Control Components - Shown On Engine 119
Task
Ensuring knock-free operation of the engine with different fuels in all operating conditions from idling speed up
to maximum speed of engine, from an engine load of more than approx. 40%. For this purpose, if uncontrolled
combustion (knocking) occurs, the ignition angle at the relevant cylinder or cylinders is retarded.
Design/function
The anti-knock control (AKC) function is integrated in the ME-SFI control unit. The range of functions has
been enlarged compared to previous versions.
Input signals:
Engine speed (crankshaft position sensor)
2001 Mercedes-Benz ML320
1998-2005 ENGINE Electrical System - Engine - 163 Chassis
me
Camshaft position (camshaft Hall sensor)
Knock identification:
Engine 104, 111, 112, 113, 119, 120 by means of knock sensors Engine 137 by ionic current
measurement
Engine temperature (coolant temperature sensor)
Engine load (hot film air flow sensor or pressure sensor on supercharged engines)
Accelerator pedal position (accelerator pedal sensor)
Precontrol by means of automatic RON switch (internal)
Output signals:
Cylinder specific ignition angle correction on the calculated map value of the ME control unit.
Ignition angle emergency mode if fault identified.
Basic function
The anti-knock control is active from a coolant temperature of 70 °C. If knocking is detected at a cylinder above
an engine load of approx. 40%, its ignition angle is retarded from the next ignition by about 2.3° crank angle
(e.g. M119) or by about 3.0° crank angle (e.g. M120). If knocking continues to be detected, the ignition angle is
continuously retarded in steps of 2.3° crank angle (e.g. M119) until the maximum retardation is reached
(approx. 10 to 15° crank angle, depending on engine speed). In addition, the automatic RON switch influences
the maximum retarding of the ignition timing - the higher the selected RON stage, the less is the maximum
retarding of the ignition timing.
If knocking-free combustion exists, the retardation is reduced in steps of approx. 0.75° crank angle after a few
ignitions (depending on engine speed) until the map value (a) is achieved, or knocking once again occurs.
Adaptation of anti-knock control
The adaptation of the anti-knock control is active from a coolant temperature of approx. 75 °C. Any corrections
required to the ignition angle because of knocking combustion are constantly detected for the specific cylinder
and stored together with the relevant operating state of the engine (engine load/speed range).
The stored adaptation value is taken into account in the output of the individual cylinder angle so that each
cylinder is immediately operated with the optimal ignition angle.
During abrupt acceleration, no values are stored for about 2 seconds in order to avoid any incorrect adaptation
values.
Faults in the case of knocking detection
If no signals are received from the knock sensors or from the ionic current measurement, the ignition angle of
all the cylinders is retarded, for safety reasons, by as much as approx. 11° crank angle depending on engine
2001 Mercedes-Benz ML320
1998-2005 ENGINE Electrical System - Engine - 163 Chassis
me
speed and temperature. The anti-knock control and the adaptation are deactivated and a fault is stored.
Automatic RON switch
In addition to the RON correction using the HHT, the anti-knock control features an automatic RON switch.
This detects a persistent high knocking tendency of the engine and assists the anti-knock control by means of an
appropriate pre-control.
This is done by analyzing the stored adaptation values, the ignition angles of all the cylinders and the number of
control interventions in certain engine load and speed ranges. Depending on the threshold which has been
exceeded, the RON value is adjusted by one or several stages. The value is retained until the engine is switched
off.
After engine start, only the RON correction which is carried out by means of the HHT/STAR DIAGNOSIS is at
first active.
KNOCK SENSORS, LOCATION - GF15.12-P-4101-01A
Crankshaft position sensor,
location/task/ design/function
GF07.04-P-4116F
Camshaft Hall sensor,
location/task/design/ function
GF07.04-P-4117F
Knock sensors,
location/task/design/function
GF15.12-P-4101F
Coolant temperature sensor,
location/task/ design/function
Engine 119, 120
GF07.04-P-5026F
Engine 104, 111
GF07.04-P-5026G
Engine 112, 113, 137
GF07.04-P-5026A
Hot film mass air flow sensor,
location/task/ design/function
Engine 119, 120 (round
connector)
GF07.07-P-4118E
Engine 104, 111, 112,
113, 137
GF07.07-P-4118G
Engine 111 EVO
GF07.07-P-4118GS
Pedal value sensor,
location/task/design/ function
GF30.20-P-4011L
ME-SFI control unit
position/task/design/ function
GF07.61-P-5000F
Engine 111 EVO
GF07.61-P-5000GS
ME-SFI synchronizing fuel
injection and firing order function
GF07.61-P-4009F
Engine 111 EVO
GF07.61-P-4009GS
2001 Mercedes-Benz ML320
1998-2005 ENGINE Electrical System - Engine - 163 Chassis
me
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